Hypersensitive aba receptors

ABSTRACT

Hypersensitive PYR/PYL polypeptides, compositions, and methods are provided.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

The present patent application is a continuation-in-part ofPCT/US2015/047020, filed Aug. 26, 2015, which claims benefit of priorityto U.S. Provisional Patent Application No. 62/042,095, filed Aug. 26,2014 and U.S. Provisional Patent Application No. 62/098,025, filed Dec.30, 2014, which are incorporated by reference for all purposes.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH AND DEVELOPMENT

This invention was made with Government support under Grant No. 1258175awarded by the National Science Foundation. The Government has certainrights in this invention.

BACKGROUND OF THE INVENTION

Abscisic acid (ABA) is a plant hormone that regulates signaltransduction associated with abiotic stress responses Cutler, S. R., etal. Annu. Rev. Plant Biol. 61, 651-679 (2010)). The ABA signalingpathway has been exploited to improve plant stress response andassociated yield traits via numerous approaches (Wang, Y., et al. PlantJ. 43, 413-424 (2005)). The direct application of ABA to plants improvestheir water use efficiency (Rademacher, W., Maisch, R., Liessegang, J.,& Jung, J. (1987). Water consumption and yield formation in crop plantsunder the influence of synthetic analogues of abscisic acid. Plantgrowth regulators for agricultural and amenity use. BCPC Monograph,(36), 53-66); for this reason, the discovery of ABA agonists (Okamoto,M., et al., Proc. Natl. Acad. Sci. U.S.A 110, 12132-12137 (2013); Park,S.-Y., et al. Science 324, 1068-1071 (2009)) has received increasingattention, as such molecules may be beneficial for improving crop yield.A complementary approach to activating the ABA pathway involvesincreasing a plant's sensitivity to ABA via genetic methods. Forexample, conditional antisense of farnesyl transferase beta subunitgene, which increases a plant's ABA sensitivity, improves yield undermoderate drought in both canola and Arabidopsis (Wang et al., 2005).

It has recently been discovered that ABA elicits many of its cellularresponses by binding to a soluble family of receptors called PYR/PYLproteins. PYR/PYL proteins belong to a large family of ligand-bindingproteins named the START superfamily (Iyer, L. M., et al., ProteinsStruct. Funct. Bioinforma. 43, 134-144, 2001; Ponting, C. P., andAravind, L. (1999). Trends Biochem. Sci. 24, 130-132 1999). Theseproteins contain a conserved three-dimensional architecture consistingof seven anti-parallel beta sheets, which surround a central alpha helixto form a “helix-grip” motif; together, these structural elements form aligand-binding pocket for binding ABA or other agonists.

Structural and functional studies have uncovered a series ofconformational changes and critical contacts between PYR/PYL receptorsand type II C protein phosphatases (PP2Cs) that are necessary forABA-mediated PP2C inhibition by receptors. For example, when ABA oranother agonist binds within the ligand-binding pockets of PYR/PYLproteins, it stabilizes a conformational change that allows thereceptors to bind and inhibit a family of PP2Cs that normally repressABA signaling (Weiner et al., 2010). In particular, ABA binding leads toa large rearrangement in a flexible “gate” loop that flanks theligand-binding pocket. Upon ABA binding, the gate loop adopts a closedconformation that is stabilized by several direct contacts between theloop and ABA. This agonist-bound, closed form of the gate allows PYR/PYLproteins to dock into, and inhibit, the active site of PP2Cs. Theresulting inhibition in turn allows activation of downstream kinases inthe SnRK2 class, which are responsible for the regulation of theactivity of transcription factors, ion channels and other proteinsinvolved in ABA responses (Weiner, J. J., et al. (2010) Curr. Opin.Plant Biol. 13, 495-5022010). Thus, the stabilization of a closed gateconformation of the receptors plays a role in their activation andPYR/PYL receptors are molecular switches at the apex of a signalingcascade that regulates diverse ABA responses.

In addition to the role that gate closure plays in receptor activation,other structural rearrangements also occur. For example, PYR1, PYL1, andPYL2 are homodimers in solution, but bind to PP2Cs as monomers. Thehomodimer interface overlaps with the PP2C binding interface andtherefore an intact receptor homodimer cannot bind to and inhibit thePP2C. Thus, dimer formation is antagonistic to ABA signaling andreceptor dimer-breaking is a necessary step in receptor activation.Additionally, a recognition module containing a central conservedtryptophan “lock” residue located on the PP2C inserts into a small poreformed in the ABA-bound receptors. Mutation of the tryptophan lockresidue abolishes receptor-mediated inactivation of PP2C activity,demonstrating a role of the lock residue's insertion into the receptor'spore.

Over-expression of wild type or mutant ABA receptors in transgenicArabidopsis thaliana, Solanum lycopersicum and Oryza sativa improvesdrought tolerance (Gonzalez-Guzman, M., et al. (2014). J. Exp. Bot.eru219, 2014; Kim et al., J. Exp. Bot. 63, 1013-1024 2012; Santiago etal., Plant J. 60, 575-588 (2009)). ABA receptors with increasedsensitivity relative to their wild type counterparts can elicit greaterABA responses when expressed in planta. Consistent with this, Pizzio etal., Plant Physiol. 163, 441-455 (2013) described the PYL4 mutationA194T mutant, which requires lower concentrations of ABA to elicitmeasured ABA responses in comparison to wild type PYL4. When this mutantis over-expressed in transgenic Arabidopsis, the plants have increasedsensitivity to ABA relative to both wild type controls and PYL4over-expression controls (Pizzio et al., Plant Physiol. 163, 441-455(2013)). Moreover, the 35S::PYL4^(A194T) lines display better droughttolerance and water use than wild type or 35S::PYL4 overexpressionlines. The A194T mutation is located in PYL4's carboxyl terminus, whichis a part of the receptors that is highly variable in length andcomposition between receptors. This lack of conservation makes itdifficult to predict the mechanism by which the mutation alters ABAsensitivity.

BRIEF SUMMARY OF THE INVENTION

Mutations in PYR/PYL receptor proteins have been identified that resultin the receptor proteins being hypersensitive to ABA. In someembodiments, nucleic acids (e.g., isolated) encoding such proteins areprovided. In some embodiments, the nucleic acids comprises apolynucleotide encoding a mutated PYR/PYL receptor polypeptidecomprising an amino acid substitution corresponding to the amino acidF61, V81, I110, E141, and A160 in PYR1 as set forth in SEQ ID NO:1,wherein the mutated PYR/PYL receptor has increased sensitivity toabscisic acid compared to a control PYR/PYL receptor lacking thesubstitution.

In some embodiments, the PYR/PYL receptor polypeptide comprises an aminoacid substitution corresponding to the amino acid F61. In someembodiments, the amino acid substitution is selected from L and M.

In some embodiments, the PYR/PYL receptor polypeptide comprises an aminoacid substitution corresponding to the amino acid V81. In someembodiments, the amino acid substitution is selected from I and Y.

In some embodiments, the PYR/PYL receptor polypeptide comprises an aminoacid substitution corresponding to the amino acid I110. In someembodiments, the amino acid substitution is selected from C and S.

In some embodiments, the PYR/PYL receptor polypeptide comprises an aminoacid substitution corresponding to the amino acid E141. In someembodiments, the amino acid substitution is selected from C, I, L, M, N,T, V, W, and Y.

In some embodiments, the PYR/PYL receptor polypeptide comprises an aminoacid substitution corresponding to the amino acid A160. In someembodiments, the amino acid substitution is selected from C, I, and V.

In some embodiments, the PYR/PYL receptor polypeptide comprises an aminoacid substitution corresponding to:

F61L and A160C; F61M and A160V; F61M, I110S, and A160V; or F61L, V81I,I110C and A160V.

In some embodiments, the mutated PYR/PYL receptor polypeptide issubstantially identical to (e.g., at least 50%, 55%, 60%, 65%, 70%, 75%,80%, 85%, 90%, 91%, 92%, 93%, 94% 95%, 96%, 97%, 98%, or 99% identicalto) any of SEQ ID NOs:1-119 or SEQ ID NOs:124-154 (e.g., 124, 125, 126,127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140,141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, or154), 155-361 (e.g., 155, 156, 157, 158, 159, 160, 161, 162, 163, 164,165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178,179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192,193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206,207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220,221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234,235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248,249, 250, 251, 252, 253, 254, 255, 256, 257, 258, 259, 260, 261, 262,263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 273, 274, 275, 276,277, 278, 279, 280, 281, 282, 283, 284, 285, 286, 287, 288, 289, 290,291, 292, 293, 294, 295, 296, 297, 298, 299, 300, 301, 302, 303, 304,305, 306, 307, 308, 309, 310, 311, 312, 313, 314, 315, 316, 317, 318,319, 320, 321, 322, 323, 324, 325, 326, 327, 328, 329, 330, 331, 332,333, 334, 335, 336, 337, 338, 339, 340, 341, 342, 343, 344, 345, 346,347, 348, 349, 350, 351, 352, 353, 354, 355, 356, 357, 358, 359, 360, or361) or comprises any of SEQ ID NOs: 120-123.

Also provided is a plant (e.g. a transgenic or non-transgenic plant)comprising a polynucleotide encoding a PYR/PYL receptor polypeptide asdescribed above or elsewhere herein, e.g., comprising an amino acidsubstitution corresponding to the amino acid F61, V81, I110, E141, andA160 in PYR1 as set forth in SEQ ID NO:1. In some embodiments, the plantwill have increased sensitivity to ABA compared to a control plantlacking the polypeptide. In some embodiments, the polynucleotide isoperably linked to a heterologous promoter. In some embodiments, thepolynucleotide is operably linked to a native (non-heterologous)promoter. In some embodiments, the PYR/PYL receptor polypeptidecomprises an amino acid substitution corresponding to: F61L and A160C;F61M and A160V; F61M, I110S, and A160V; or F61L, V81I, I110C and A160V.In some embodiments, the encoded PYR/PYL receptor polypeptide only hasone (or in some embodiments, only 2, 3, or 4) amino acid substitutioncompared to the plant's native PYR/PYL receptor polypeptide. In someembodiments, the plant's native PYR/PYL receptor polypeptide codingsequence has been modified (e.g., by CRISPR) to contain the 1, 2, 3, or4 substitutions. In some embodiments, the PYR/PYL receptor polypeptidecomprises an amino acid substitution corresponding to the amino acidF61. In some embodiments, the amino acid substitution is selected from Land M. In some embodiments, the PYR/PYL receptor polypeptide comprisesan amino acid substitution corresponding to the amino acid V81. In someembodiments, the amino acid substitution is selected from I and Y. Insome embodiments, the PYR/PYL receptor polypeptide comprises an aminoacid substitution corresponding to the amino acid I110. In someembodiments, the amino acid substitution is selected from C and S. Insome embodiments, the PYR/PYL receptor polypeptide comprises an aminoacid substitution corresponding to the amino acid E141. In someembodiments, the amino acid substitution is selected from C, I, L, M, N,T, V, W, and Y. In some embodiments, the PYR/PYL receptor polypeptidecomprises an amino acid substitution corresponding to the amino acidA160. In some embodiments, the amino acid substitution is selected fromC, I, and V. In some embodiments, the PYR/PYL receptor polypeptidecomprises an amino acid substitution corresponding to: F61L and A160C;F61M and A160V; F61M, I110S, and A160V; or F61L, V81I, I110C and A160V.

Also provided is a plant (e.g., including but not limited to a maizeplant) comprising an in situ mutated PYR/PYL receptor polypeptidecomprising an amino acid substitution corresponding to the amino acidF61, V81, I110, E141, and A160 in PYR1 as set forth in SEQ ID NO:1,wherein the mutated PYR/PYL receptor polypeptide has increasedsensitivity to abscisic acid compared to a control PYR/PYL receptorlacking the substitution. In some embodiments, the PYR/PYL receptorpolypeptide comprises an amino acid substitution corresponding to theamino acid F61. In some embodiments, the amino acid substitution isselected from L and M. In some embodiments, the PYR/PYL receptorpolypeptide comprises an amino acid substitution corresponding to theamino acid V81. In some embodiments, the amino acid substitution isselected from I and Y. In some embodiments, the PYR/PYL receptorpolypeptide comprises an amino acid substitution corresponding to theamino acid I110. In some embodiments, the amino acid substitution isselected from C and S. In some embodiments, the PYR/PYL receptorpolypeptide comprises an amino acid substitution corresponding to theamino acid E141. In some embodiments, the amino acid substitution isselected from C, I, L, M, N, T, V, W, and Y. In some embodiments, thePYR/PYL receptor polypeptide comprises an amino acid substitutioncorresponding to the amino acid A160. In some embodiments, the aminoacid substitution is selected from C, I, and V. In some embodiments, thePYR/PYL receptor polypeptide comprises an amino acid substitutioncorresponding to: F61L and A160C; F61M and A160V; F61M, I110S, andA160V; or F61L, V81I, I110C and A160V. In some embodiments, the mutatedPYR/PYL receptor polypeptide is substantially identical to (e.g., atleast 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%95%, 96%, 97%, 98%, or 99% identical to) any of SEQ ID NOs:1-119 or SEQID NOs:124-154 (e.g., 124, 125, 126, 127, 128, 129, 130, 131, 132, 133,134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147,148, 149, 150, 151, 152, 153, or 154), 155-361 (e.g., 155, 156, 157,158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171,172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185,186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199,200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213,214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227,228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241,242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255,256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266, 267, 268, 269,270, 271, 272, 273, 274, 275, 276, 277, 278, 279, 280, 281, 282, 283,284, 285, 286, 287, 288, 289, 290, 291, 292, 293, 294, 295, 296, 297,298, 299, 300, 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 311,312, 313, 314, 315, 316, 317, 318, 319, 320, 321, 322, 323, 324, 325,326, 327, 328, 329, 330, 331, 332, 333, 334, 335, 336, 337, 338, 339,340, 341, 342, 343, 344, 345, 346, 347, 348, 349, 350, 351, 352, 353,354, 355, 356, 357, 358, 359, 360, or 361) or comprises any of SEQ IDNOs: 120-123.

Also provided are expression cassettes comprising a promoter operablylinked to the polynucleotide encoding a PYR/PYL receptor polypeptide asdescribed above or elsewhere herein, e.g., comprising an amino acidsubstitution corresponding to the amino acid F61, V81, I110, E141, andA160 in PYR1 as set forth in SEQ ID NO:1, wherein introduction of theexpression cassette into a plant results in the plant having increasedsensitivity to abscisic acid compared to a control plant lacking theexpression cassette.

In some embodiments, the promoter is heterologous to the polynucleotide.In some embodiments, the promoter is inducible. In some embodiments, thepromoter is a stress-inducible promoter.

Also provided is an expression vector comprising the expression cassetteas described above or elsewhere herein.

Also provided are plants comprising an expression cassette as describedabove or elsewhere herein, wherein the plant has increased sensitivityto abscisic acid compared to a control plant lacking the expressioncassette. Also provided is a plant cell from the plant.

Also provided is a seed, flower, leaf, fruit, processed food, or foodingredient from a plant comprising a hypersensitive a PYR/PYL receptorpolypeptide as described herein.

Also provided is a method of producing a plant having increasedsensitivity to abscisic acid. In some embodiments, the method comprises:introducing the expression cassette encoding a hypersensitive a PYR/PYLreceptor polypeptide as described herein into a plurality of plants; andselecting a plant that expresses the polynucleotide from the pluralityof plants.

In some embodiments, the method comprises: introducing a mutation into apolynucleotide encoding a hypersensitive PYR/PYL polypeptide asdescribed herein, e.g., wherein the mutation results in a polynucleotideencoding an amino acid substitution corresponding to the amino acid F61,V81, I110, E141, and A160 in PYR1 as set forth in SEQ ID NO:1. In someembodiments, the introducing occurs in situ in the genome of a plantcell. In some embodiments, the introducing comprises clustered regularlyinterspaced short palindromic repeats (CRISPR)/Cas genome editing.

Provided herein are methods and reagents for producing a plant (e.g., amaize plant) having increased sensitivity to abscisic acid, the methodincludes introducing a mutation into a polynucleotide encoding a PYR/PYLpolypeptide, where the mutation is introduced in situ in the genome ofthe plant using RNA directed genome modification methods.

In one aspect, provided herein is a guide ribonucleic acid (gRNA). Incertain embodiments the gRNA includes a CRISPR ribonucleic acid (crRNA)that is substantially identical to SEQ ID NOS: 363, 364, 365, 366, 367or 369; and a transacting ribonucleic acid (tracRNA), where the PYR/PYLmutation target site comprises a nucleic acid that encodes for V89 ofPYL-E or E149 of PYL-E.

In some embodiments of the gRNA, the PYR/PYL mutation target siteincludes a nucleic acid that encodes for V89 of PYL-E. In someembodiments, the PYR/PYL mutation target site has the sequence of SEQ IDNO:362.

In some embodiments, the PYR/PYL mutation target site includes a nucleicacid that encodes for E149 of PYL-E. In certain embodiments, the PYR/PYLmutation target site has the sequence of SEQ ID NO:368.

In certain embodiments, the tracRNA is linked to the 3′ end of the gRNA.In specific embodiments, the tracRNA is encoded by a nucleotide having asequence that is substantially identical to SEQ ID NO: 370.

In another aspect, provided herein is an isolated nucleic acid thatincludes a polynucleotide encoding any one of the gRNAs describedherein.

In another aspect, provided herein is an expression cassette thatincludes an RNA polymerase promoter operably linked to a polynucleotideencoding any one of the gRNAs described herein. In certain embodiments,the RNA polymerase promoter is an RNA polymerase III (polIII) promoter.In specific embodiments, the polIII promoter is a U3 promoter or a U6promoter. In some embodiments, the expression cassette has the sequenceof any one of SEQ ID NOS:371-373.

In another aspect, provided herein is an expression vector that includesan expression cassette, where the expression cassette includes an RNApolymerase promoter operably linked to a polynucleotide encoding any oneof the gRNAs described herein.

In another aspect, provided herein is an expression vector that includesa first expression cassette and a second expression cassette. In certainembodiments, the first expression cassette is an expression cassettethat includes an RNA polymerase promoter operably linked to apolynucleotide encoding any one of the gRNAs described herein and thesecond expression cassette is an expression cassette comprising apromoter operably linked to a polynucleotide encoding aCRISPR-associated endonuclease 9 (Cas9). In some embodiments, theexpression vector includes a third expression cassette, wherein thethird expression cassette is an expression cassette that includes an RNApolymerase promoter operably linked to a polynucleotide encoding any oneof the gRNAs described herein, and the third expression cassette isdifferent than the first expression cassette.

In some embodiments, the expression vector includes a first, second andthird expression cassette, where the first expression cassette is anexpression cassette that includes a promoter operably linked to apolynucleotide encoding a CRISPR-associated endonuclease 9 (Cas9), thesecond expression cassette has a sequence that is substantiallyidentical to SEQ ID NO: 371 or SEQ ID NO:372, and the third expressioncassette has a sequence that is substantially identical to SEQ IDNO:373. In certain embodiments, the promoter operably linked to thepolynucleotide encoding Cas9 is an ubiquitin-1 promoter (prUbi-10).

In another aspect, provided herein is a cell that includes any of theexpression vectors described above or elsewhere herein.

Also provided is a plant that includes an expression vector as describedabove or elsewhere herein. In some embodiments, the plant is a maizeplant.

Also provided is a plant cell from the plant described above orelsewhere herein.

In another aspect, provided herein is a seed, flower, leaf, fruit,processed food, or food ingredient from the plant described above orelsewhere herein. In certain embodiments, the introduction of theexpression vector into the plant described above or elsewhere hereinresults in the plant having increased sensitivity to abscisic acidcompared to a control plant lacking the expression cassette.

In another aspect, provided herein is a method of producing a planthaving a mutation at a genomic PYR/PYL mutation target site. In someembodiments the method includes introducing into plant cells anexpression vector that includes a polynucleotide encoding a gRNA and aCas9 as described above or elsewhere herein and at least one repairnucleic acid comprising the mutation. In certain embodiments, themutation is introduced in the genomic PYR/PYLR mutation target site by ahomologous recombination upon a Cas9 cleavage event in the genomicPYR/PYLR mutation target site. In some embodiments, the method furtherincludes selecting plant cells having the mutation; thereby producingthe plant. In some embodiments, the introducing occurs in situ in thegenome of a plant cell. In some embodiments, the mutation is introducedby introducing into a plant embryo cell the expression vector and atleast one repair nucleic acid, where the genome of the plant embryocomprises the PYR/PYL mutation target site and where the repair nucleicacid comprises the mutation and introduces the mutation at the PYR/PYLmutation target site by homologous recombination upon a Cas9 cleavageevent in the PYL-E mutation target site.

In some embodiments, the repair nucleic acid has a sequence that issubstantially identical to any one of the sequence of SEQ ID NOS:375 to387 In certain embodiments, the repair nucleic acid has a sequence thatis substantially identical to SEQ ID NO:377. In some embodiments, therepair nucleic acid has a sequence that is substantially identical tothe sequence of SEQ ID NO:387. In other embodiments, two repair nucleicacids are introduced, and wherein the repair nucleic acids havesequences that are substantially identical to SEQ ID NO:377 and SEQ IDNO:379. In specific embodiments, the plant is a maize plant.

In another aspect, provided herein is a kit that includes an expressionvector of that includes a polynucleotide encoding a gRNA and apolynucleotide encoding a Cas9 as described above or elsewhere hereinand at least one repair nucleic acid, wherein the repair nucleic acidcomprises a PYL-E mutation and is capable of introducing the PYL-Emutation in situ in a plant cell genome by homologous recombination upona Cas9 cleavage event. In some embodiments, the at least one repairnucleic acid has a sequence that is substantially identical to SEQ IDNOS::374 to 386.

In another aspect, provided herein is an isolated nucleic acidcomprising a polynucleotide encoding a mutated PYR/PYL receptorpolypeptide comprising an amino acid substitution corresponding to theamino acid V89 in PYL-E, wherein the amino acid substitution is A (SEQID NO:389). In some embodiments, the mutated PYR/PYL receptorpolypeptide further comprises an amino acid substitution correspondingto the amino acid E149. In certain embodiments the amino acidsubstitution corresponding to the amino acid E149 is L (SEQ ID NO:390).

In yet another aspect, provided herein is an isolated nucleic acidcomprising a polynucleotide encoding a fusion protein comprising amutated PYR/PYL receptor polypeptide and a fusion partner polypeptide,wherein the mutated PYR/PYL receptor polypeptide comprises an amino acidsubstitution corresponding to the amino acid V89 in PYL-E, wherein theamino acid substitution is A. In certain embodiments, the mutatedPYR/PYL receptor polypeptide further comprises an amino acidsubstitution corresponding to the amino acid E149. In specificembodiments, the amino acid substitution corresponding to the amino acidE149 is L.

In some embodiments, the fusion partner polypeptide includes atranscription activation domain or a transcription modulation domain. Incertain embodiments, the transcription activation domain is VP16 orVP64. In certain embodiments, the fusion protein further comprises anuclear localization signal sequence. In some embodiments, the mutatedPYR/PYL receptor polypeptide has increased sensitivity to abscisic acidcompared to a control PYR/PYL receptor polypeptide lacking thesubstitution.

Provided herein is a cell comprising a polynucleotide as described aboveor elsewhere herein. In certain embodiments, the polynucleotide is aheterologous polypeptide. In some embodiments, the cell is a non-planteukaryotic cell.

In yet another embodiment, provided herein is a plant that includes apolynucleotide as described above or elsewhere herein. In certainembodiments, the plant is a maize plant.

In another embodiment, provided herein is an expression cassettecomprising a promoter operably linked to a polynucleotide as describedabove or elsewhere herein. In some embodiments, the promoter isheterologous to the polynucleotide. In certain embodiments, the promoteris inducible. In some embodiments, the promoter is a stress-induciblepromoter.

In another embodiment, provided herein is an expression vectorcomprising the expression cassette as described above or elsewhereherein.

In another aspect, provided herein is a plant that includes theexpression cassette as described above or elsewhere herein. In anotheraspect, provided herein is a plant cell from the plant as describedabove or elsewhere herein. In yet another aspect, provided herein is aseed, flower, leaf, fruit, processed food, or food ingredient from theplant as described above or elsewhere herein.

Other aspects of the invention are described elsewhere herein.

DEFINITIONS

The term “PYR/PYL receptor polypeptide” refers to a proteincharacterized in part by the presence of one or more or all of apolyketide cyclase domain 2 (PF10604), a polyketide cyclase domain 1(PF03364), and a Bet V I domain (PF03364), which in wild-type formmediates abscisic acid (ABA) and ABA analog signaling. A wide variety ofPYR/PYL receptor polypeptide sequences are known in the art. In someembodiments, a PYR/PYL receptor polypeptide comprises a polypeptide thatis substantially identical to PYR1 (SEQ ID NO:1), PYL1 (SEQ ID NO:2),PYL2 (SEQ ID NO:3), PYL3 (SEQ ID NO:4), PYL4 (SEQ ID NO:5), PYL5 (SEQ IDNO:6), PYL6 (SEQ ID NO:7), PYL7 (SEQ ID NO:8), PYL8 (SEQ ID NO:9), PYL9(SEQ ID NO:10), PYL10 (SEQ ID NO:11), PYL11 (SEQ ID NO:12), PYL12 (SEQID NO:13), or PYL13 (SEQ ID NO:14), or to any of SEQ ID NOs:15-119.

A “wild-type PYR/PYL receptor polypeptide” refers to a naturallyoccurring PYR/PYL receptor polypeptide that mediates abscisic acid (ABA)and ABA analog signaling.

A “mutated PYR/PYL receptor polypeptide” refers to a PYR/PYL receptorpolypeptide that is a variant from a naturally-occurring (i.e.,wild-type) PYR/PYL receptor polypeptide. As used herein, a mutatedPYR/PYL receptor polypeptide comprises one, two, three, four, or moreamino acid substitutions relative to a corresponding wild-type PYR/PYLreceptor polypeptide while retaining ABA-responsiveness of the receptor.In this context, a “mutated” polypeptide can be generated by any methodfor generating non-wild type nucleotide sequences. In some embodiments,a mutated PYR/PYL receptor polypeptide is hypersensitive, meaning themutant receptor polypeptide is activated by ABA more strongly than acorresponding homologous wildtype receptor (or at least compared to anotherwise identical PYR/PYL polypeptide having the wildtype amino acidat the mutated position described herein) would be activated by the sameconcentration of ABA, or that the mutant receptor polypeptide isactivated by a lower (e.g., half or less of the) concentration of ABAthan activates the corresponding homologous wild-type receptor, or both.In some embodiments, the mutant receptor polypeptide can be determinedvisually in a HAB1 yeast two-hybrid assay to respond to 0.25 μM or lessABA.

An “amino acid substitution” refers to replacing the naturally occurringamino acid residue in a given position (e.g., the naturally occurringamino acid residue that occurs in a wild-type PYR/PYL receptorpolypeptide) with an amino acid residue other than thenaturally-occurring residue. For example, the naturally occurring aminoacid residue at position 60 of the wild-type PYR1 receptor polypeptidesequence (SEQ ID NO:1) is histidine (H60); accordingly, an amino acidsubstitution at H60 refers to replacing the naturally occurringhistidine with any amino acid residue other than histidine.

An amino acid residue “corresponding to an amino acid residue [X] in[specified sequence,” or an amino acid substitution “corresponding to anamino acid substitution [X] in [specified sequence]” refers to an aminoacid in a polypeptide of interest that aligns with the equivalent aminoacid of a specified sequence. Generally, as described herein, the aminoacid corresponding to a position of a specified PYR/PYL receptorpolypeptide sequence can be determined using an alignment algorithm suchas BLAST. In some embodiments of the present invention, “correspondence”of amino acid positions is determined by aligning to a region of thePYR/PYL receptor polypeptide comprising SEQ ID NO:1, as discussedfurther herein. When a PYR/PYL receptor polypeptide sequence differsfrom SEQ ID NO:1 (e.g., by changes in amino acids or addition ordeletion of amino acids), it may be that a particular mutationassociated with hypersensitive activity of the PYR/PYL receptor will notbe in the same position number as it is in SEQ ID NO:1. For example,amino acid position V85 of PYL2 (SEQ ID NO:3) aligns with amino acidposition V81 of PYR1 (SEQ ID NO:1), as can be readily illustrated in analignment of the two sequences. In this example, amino acid position 85in SEQ ID NO:3 corresponds to position 81 in SEQ ID NO:1. Examples ofcorresponding positions are shown in FIG. 2

Two nucleic acid sequences or polypeptides are said to be “identical” ifthe sequence of nucleotides or amino acid residues, respectively, in thetwo sequences is the same when aligned for maximum correspondence asdescribed below. The terms “identical” or percent “identity,” in thecontext of two or more nucleic acids or polypeptide sequences, refer totwo or more sequences or subsequences that are the same or have aspecified percentage of amino acid residues or nucleotides that are thesame, when compared and aligned for maximum correspondence over acomparison window, as measured using one of the following sequencecomparison algorithms or by manual alignment and visual inspection. Whenpercentage of sequence identity is used in reference to proteins orpeptides, it is recognized that residue positions that are not identicaloften differ by conservative amino acid substitutions, where amino acidsresidues are substituted for other amino acid residues with similarchemical properties (e.g., charge or hydrophobicity) and therefore donot change the functional properties of the molecule. Where sequencesdiffer in conservative substitutions, the percent sequence identity maybe adjusted upwards to correct for the conservative nature of thesubstitution. Means for making this adjustment are well known to thoseof skill in the art. Typically this involves scoring a conservativesubstitution as a partial rather than a full mismatch, therebyincreasing the percentage sequence identity. Thus, for example, where anidentical amino acid is given a score of 1 and a non-conservativesubstitution is given a score of zero, a conservative substitution isgiven a score between zero and 1. The scoring of conservativesubstitutions is calculated according to, e.g., the algorithm of Meyers& Miller, Computer Applic. Biol. Sci. 4:11-17 (1988) e.g., asimplemented in the program PC/GENE (Intelligenetics, Mountain View,Calif., USA).

The phrase “substantial identity” or “substantially identical,” used inthe context of two nucleic acids or polypeptides, refers to a sequencethat has at least 50% sequence identity with a reference sequence.Alternatively, percent identity can be any integer from 50% to 100%. Insome embodiments, a sequence is substantially identical to a referencesequence if the sequence has at least 50%, 55%, 60%, 65%, 70%, 75%, 80%,85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequenceidentity to the reference sequence as determined using the methodsdescribed herein; preferably BLAST using standard parameters, asdescribed below. Embodiments of the present invention provide fornucleic acids encoding polypeptides that are substantially identical toany of SEQ ID NO:1-119 or SEQ ID NOs:155-361.

For sequence comparison, typically one sequence acts as a referencesequence, to which test sequences are compared. When using a sequencecomparison algorithm, test and reference sequences are entered into acomputer, subsequence coordinates are designated, if necessary, andsequence algorithm program parameters are designated. Default programparameters can be used, or alternative parameters can be designated. Thesequence comparison algorithm then calculates the percent sequenceidentities for the test sequences relative to the reference sequence,based on the program parameters.

A “comparison window,” as used herein, includes reference to a segmentof any one of the number of contiguous positions selected from the groupconsisting of from 20 to 600, usually about 50 to about 200, moreusually about 100 to about 150 in which a sequence may be compared to areference sequence of the same number of contiguous positions after thetwo sequences are optimally aligned. Methods of alignment of sequencesfor comparison are well-known in the art. Optimal alignment of sequencesfor comparison can be conducted, e.g., by the local homology algorithmof Smith & Waterman, Adv. Appl. Math. 2:482 (1981), by the homologyalignment algorithm of Needleman & Wunsch, J. Mol. Biol. 48:443 (1970),by the search for similarity method of Pearson & Lipman, Proc. Nat'l.Acad. Sci. USA 85:2444 (1988), by computerized implementations of thesealgorithms (GAP, BESTFIT, FASTA, and TFASTA in the Wisconsin GeneticsSoftware Package, Genetics Computer Group, 575 Science Dr., Madison,Wis.), or by manual alignment and visual inspection.

Algorithms that are suitable for determining percent sequence identityand sequence similarity are the BLAST and BLAST 2.0 algorithms, whichare described in Altschul et al. (1990)J. Mol. Biol. 215: 403-410 andAltschul et al. (1977) Nucleic Acids Res. 25: 3389-3402, respectively.Software for performing BLAST analyses is publicly available through theNational Center for Biotechnology Information (NCBI) web site. Thealgorithm involves first identifying high scoring sequence pairs (HSPs)by identifying short words of length W in the query sequence, whicheither match or satisfy some positive-valued threshold score T whenaligned with a word of the same length in a database sequence. T isreferred to as the neighborhood word score threshold (Altschul et al,supra). These initial neighborhood word hits acts as seeds forinitiating searches to find longer HSPs containing them. The word hitsare then extended in both directions along each sequence for as far asthe cumulative alignment score can be increased. Cumulative scores arecalculated using, for nucleotide sequences, the parameters M (rewardscore for a pair of matching residues; always >0) and N (penalty scorefor mismatching residues; always <0). For amino acid sequences, ascoring matrix is used to calculate the cumulative score. Extension ofthe word hits in each direction are halted when: the cumulativealignment score falls off by the quantity X from its maximum achievedvalue; the cumulative score goes to zero or below, due to theaccumulation of one or more negative-scoring residue alignments; or theend of either sequence is reached. The BLAST algorithm parameters W, T,and X determine the sensitivity and speed of the alignment. The BLASTNprogram (for nucleotide sequences) uses as defaults a word size (W) of28, an expectation (E) of 10, M=1, N=−2, and a comparison of bothstrands. For amino acid sequences, the BLASTP program uses as defaults aword size (W) of 3, an expectation (E) of 10, and the BLOSUM62 scoringmatrix (see Henikoff & Henikoff, Proc. Natl. Acad. Sci. USA 89:10915(1989)).

The BLAST algorithm also performs a statistical analysis of thesimilarity between two sequences (see, e.g., Karlin & Altschul, Proc.Nat'l. Acad. Sci. USA 90:5873-5787 (1993)). One measure of similarityprovided by the BLAST algorithm is the smallest sum probability (P(N)),which provides an indication of the probability by which a match betweentwo nucleotide or amino acid sequences would occur by chance. Forexample, a nucleic acid is considered similar to a reference sequence ifthe smallest sum probability in a comparison of the test nucleic acid tothe reference nucleic acid is less than about 0.01, more preferably lessthan about 10⁻⁵, and most preferably less than about 10⁻²⁰.

The term “promoter,” as used herein, refers to a polynucleotide sequencecapable of driving transcription of a coding sequence in a cell. Thus,promoters used in the polynucleotide constructs of the invention includecis-acting transcriptional control elements and regulatory sequencesthat are involved in regulating or modulating the timing and/or rate oftranscription of a gene. For example, a promoter can be a cis-actingtranscriptional control element, including an enhancer, a promoter, atranscription terminator, an origin of replication, a chromosomalintegration sequence, 5′ and 3′ untranslated regions, or an intronicsequence, which are involved in transcriptional regulation. Thesecis-acting sequences typically interact with proteins or otherbiomolecules to carry out (turn on/off, regulate, modulate, etc.) genetranscription. A “plant promoter” is a promoter capable of initiatingtranscription in plant cells. A “constitutive promoter” is one that iscapable of initiating transcription in nearly all tissue types, whereasa “tissue-specific promoter” initiates transcription only in one or afew particular tissue types.

A polynucleotide sequence is “heterologous” to an organism or a secondpolynucleotide sequence if it originates from a foreign species, or, iffrom the same species, is modified from its original form. For example,when a promoter is said to be operably linked to a heterologous codingsequence, it means that the coding sequence is derived from one specieswhereas the promoter sequence is derived another, different species; or,if both are derived from the same species, the coding sequence is notnaturally associated with the promoter (e.g., is a geneticallyengineered coding sequence, e.g., from a different gene in the samespecies, or an allele from a different ecotype or variety).

An “expression cassette” refers to a nucleic acid construct that, whenintroduced into a host cell, results in transcription and/or translationof an RNA or polypeptide, respectively. Antisense or sense constructsthat are not or cannot be translated are expressly included by thisdefinition. In the case of both expression of transgenes and suppressionof endogenous genes (e.g., by antisense, or sense suppression) one ofskill will recognize that the inserted polynucleotide sequence need notbe identical, but may be only substantially identical to a sequence ofthe gene from which it was derived. As explained herein, thesesubstantially identical variants are specifically covered by referenceto a specific nucleic acid sequence.

The term “host cell” refers to any cell capable of replicating and/ortranscribing and/or translating a heterologous polynucleotide. Thus, a“host cell” refers to any prokaryotic cell (including but not limited toE. coli) or eukaryotic cell (including but not limited to yeast cells,mammalian cells, avian cells, amphibian cells, plant cells, fish cells,and insect cells), whether located in vitro or in vivo. For example,host cells may be located in a transgenic animal or transgenic plantprokaryotic cell (including but not limited to E. coli) or eukaryoticcells (including but not limited to yeast cells, mammalian cells, aviancells, amphibian cells, plant cells, fish cells, and insect cells). Hostcells can be for example, transformed with the heterologouspolynucleotide.

The term “plant” includes whole plants, shoot vegetative organs and/orstructures (e.g., leaves, stems and tubers), roots, flowers and floralorgans (e.g., bracts, sepals, petals, stamens, carpels, anthers), ovules(including egg and central cells), seed (including zygote, embryo,endosperm, and seed coat), fruit (e.g., the mature ovary), seedlings,plant tissue (e.g., vascular tissue, ground tissue, and the like), cells(e.g., guard cells, egg cells, trichomes and the like), and progeny ofsame. The class of plants that can be used in the method of theinvention is generally as broad as the class of higher and lower plantsamenable to transformation techniques, including angiosperms(monocotyledonous and dicotyledonous plants), gymnosperms, ferns, andmulticellular algae. It includes plants of a variety of ploidy levels,including aneuploid, polyploid, diploid, haploid, and hemizygous.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides signal in a yeast two-hybrid assay with ABAconcentration shown at the top and the identity of the mutants shown onthe left side.

FIG. 2 provides the corresponding naturally-occurring amino acid at thefive positions described herein for a number of different PYR/PYLproteins.

FIG. 3 provides an alignment of the middle portion a number of PYR/PYLproteins. (SEQ ID NOs:142-154)

FIG. 4 provides signal in a yeast two-hybrid assay and includes multiplemutations within PYR1.

FIG. 5 depicts a biolistic transformation vector pZmPYLE-V89A carryingexpression cassettes for maize-optimized Cas9 and ZmPYLE-V89A gRNA tomediate cleavage at the ZmPYL-E target sequence (5′-CGCGA CGTCA ACGTCAAGAC-3′ (SEQ ID NO:362))

FIG. 6 provides a schematic map of binary vector pZmPYLE-E149L used fordelivery with Agrobacterium-mediated transformation.

FIG. 7 provides a schematic map of plasmid vector pZmPYLE-V89A-E149Lcarrying expression cassettes for 2 different gRNAs and Cas9.

FIG. 8 provides a schematic map of binary plant transformation vector23190 carrying expression cassettes for Cas9, gRNA and selectable markergene PMI for mediating ZmPYL-E E149L mutagenesis.

FIG. 9A-B provide a schematic map of binary plant transformation vectors23136 and 23189 carrying expression cassettes for Cas9, gRNA andselectable marker gene PMI for mediating ZmPYL-D E169L mutagenesis.

FIG. 10A-10B provide a schematic map of binary plant planttransformation vectors 22981 and 23191 carrying expression cassettes forCas9, gRNA and selectable marker gene PMI for mediating ZmPYL-F E164Lmutagenesis.

FIG. 11 provides a schematic map of binary plant plant transformationvector 23192 carrying expression cassettes for Cas9, gRNA and selectablemarker gene PMI for mediating ZmPYL-E E148L.

FIG. 12 provides a schematic drawing of end point assay example todetect specific DNA sequence change (GA to CT) in ZmPYL-F that resultsin E164L amino acid residue mutation.

FIG. 13 shows sequence alignment (SEQ ID NOS:414-430) of targetedmutations in ZmPYL-F mediated by gRNA-Cas9 expressed from vector 22981.

DETAILED DESCRIPTION OF THE INVENTION I. Introduction

To identify mutations causing increased receptor ABA sensitivity, wescreened for mutants that lower the concentration of ABA required toinduce a detectable interaction between PYR1 and HAB1 using a collectionof PYR1 mutants that contain all possible single amino acidsubstitutions residues located in close proximity to ABA. Based on theseresults, we describe mutations in highly-conserved residues thatsubstantially increase receptor ABA sensitivity.

Mutations in PYR/PYL receptor polypeptides have been discovered thatresult in hypersensitive forms of the PYR/PYL receptor, i.e., themutated receptors are more responsive to the ABA compared to acorresponding wildtype PYR/PYL polypeptide.

Expression in a plant of one or more hypersensitive mutant PYR/PY1receptor polypeptides as described here will result in a plant withincreased ABA-sensitivity, and in some embodiments, higher stresstolerance or other phenotypes associated with ABA-responsiveness.

Also provided herein are methods and reagents for producing a plant(e.g., a maize plant) having increased sensitivity to abscisic acid, themethod includes introducing a mutation into a polynucleotide encoding aPYR/PYL polypeptide, where the mutation is introduced in situ in thegenome of the plant using RNA directed genome modification methods.

II. Hypersensitive PYR/PYL Receptor Polypeptides

A wide variety of wild-type (naturally occurring) PYR/PYL polypeptidesequences are known in the art. Although PYR1 was originally identifiedas an abscisic acid (ABA) receptor in Arabidopsis, in fact PYR1 is amember of a group of at least 14 proteins (PYR/PYL proteins) in the sameprotein family in Arabidopsis that also mediate ABA signaling. Thisprotein family is also present in other plants (see, e.g., SEQUENCELISTING) and is characterized in part by the presence of one or more orall of a polyketide cyclase domain 2 (PF10604), a polyketide cyclasedomain 1 (PF03364), and a Bet V I domain (PF03364). START/Bet v 1superfamily domain are described in, for example, Radauer, BMC Evol.Biol. 8:286 (2008). In some embodiments, a wild-type PYR/PYL receptorpolypeptide comprises any of SEQ ID NOs:1-119. In some embodiments, awild-type PYR/PYL receptor polypeptide is substantially identical to(e.g., at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%,93%, 94% 95%, 96%, 97%, 98%, or 99% identical to) any of SEQ IDNOs:1-119.

PYR/PYL receptor proteins have a conserved START-domain ligand-bindingpocket flanked by two loops called the “gate” and the “latch” (Melcher,K. et al., Nature 462 (2009)). ABA binds to a PYR/PYL receptor proteinat the ligand-binding pocket and ABA binding induces closure of theloops to seal ABA inside the ligand-binding pocket. The ligand-bindingpocket of a PYR/PYL receptor polypeptide comprises amino acid residuesthat are in close proximity (e.g., within about 5 Å) to a PYR/PYL ligand(e.g., ABA) or a ligand-contacting water molecule when the ligand isbound to the PYR/PYL receptor. There are 25 residues that make up thePYR1 ligand-binding pocket. The residues of the ligand-binding pocketare also highly conserved among other PYR/PYL family members.

PYR/PYL receptor proteins directly bind to type 2 protein phosphatases(PP2Cs) and thus also contain a PP2C binding interface. The PP2C bindinginterface of a PYR/PYL receptor polypeptide comprises amino acidresidues that are in close proximity (e.g., within about 5 Å) to PP2Cwhen PP2C, the PYR/PYL receptor, and ABA are all bound together in aternary complex. There are 25 residues that make up the PYR1 PP2Cbinding interface. The residues of the PP2C binding interface are alsohighly conserved among other PYR/PYL family members.

Hypersensitive PYR/PYL receptor polypeptides are non-naturally-occurringvariants from naturally occurring (i.e., wild-type) PYR/PYL receptorpolypeptides, wherein the variant (mutant) PYR/PYL receptor polypeptideis able to bind to and/or inhibit the activity of a PP2C in the presenceof abscisic acid to a greater extent than a control PYR/PYL receptorpolypeptide in the presence of the same concentration of ABA.Hypersensitive active PYR/PYL receptor polypeptides as described hereincomprise one or more amino acid substitutions compared to a wild typePYR/PYL receptor polypeptide. In some embodiments, a hypersensitivePYR/PYL receptor polypeptide is substantially identical to (e.g., atleast 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%95%, 96%, 97%, 98%, or 99% identical to) any of SEQ ID NO:1, 2, 3, 4, 5,6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42,43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60,61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78,79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96,97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111,112, 113, 114, 115, 116, 117, 118, or 119 and comprises 1, 2, 3, 4, ormore mutations (e.g., amino acid substitutions) as described herein. Insome embodiments, a hypersensitive PYR/PYL receptor polypeptidecomprises SEQ ID NO:120, 121, 122, or 123 and comprises 1, 2, 3, 4, ormore mutations (e.g., amino acid substitutions) as described herein:

(SEQ ID NO: 120) CxSxxxxxxxAPxxxxWxxxxxFxxPxxxxxFxxxC (SEQ ID NO: 121)GxxRxVxxxSxxPAxxSxExLxxxD (SEQ ID NO: 122) GGxHRLxNYxS (SEQ ID NO: 123)ESxxVDxPxGxxxxxTxxFxxxxxxxNLxxL.

As shown in the Examples, it has been discovered that mutations can bemade at any of several positions in PYR/PYL receptor polypeptides resultin hypersensitivity to ABA. These positions are (corresponding to theirposition in Arabidopsis PYR1 (SEQ ID NO:1)): F61, V81, I110, E141, andA160. In some embodiments, a mutated PYR/PYL receptor polypeptidecomprises one or more (e.g., one, two, three, or four) amino acidsubstitutions corresponding to these positions. For example, in someembodiments, the mutated PYR/PYL receptor polypeptide comprises at leastthe following corresponding mutations:

F61L and A160C; F61M and A160V; F61M, I110S, and A160V; or F61L, V81I,I110C and A160V.

SEQ ID NO: 1; Arabidopsis wildtype PYR1Met Pro Ser Glu Leu Thr Pro Glu Glu Arg Ser Glu 1               5                  10Leu Lys Asn Ser Ile Ala Glu Phe His Thr Tyr Gln        15                  20Leu Asp Pro Gly Ser Cys Ser Ser Leu His Ala Gln25                  30                  35Arg Ile His Ala Pro Pro Glu Leu Val Trp Ser Ile            40                  45Val Arg Arg Phe Asp Lys Pro Gln Thr Tyr Lys His    50                  55                  60Phe Ile Lys Ser Cys Ser Val Glu Gln Asn Phe Glu                65                  70Met Arg Val Gly Cys Thr Arg Asp Val Ile Val Ile        75                  80Ser Gly Leu Pro Ala Asn Thr Ser Thr Glu Arg Leu85                  90                  95Asp Ile Leu Asp Asp Glu Arg Arg Val Thr Gly Phe            100                 105Ser Ile Ile Gly Gly Glu His Arg Leu Thr Asn Tyr    110                 115                 120Lys Ser Val Thr Thr Val His Arg Phe Glu Lys Glu                125                 130Asn Arg Ile Trp Thr Val Val Leu Glu Ser Tyr Val        135                 140Val Asp Met Pro Glu Gly Asn Ser Glu Asp Asp Thr145                 150                 155Arg Met Phe Ala Asp Thr Val Val Lys Leu Asn Leu            160                 165Gln Lys Leu Ala Thr Val Ala Glu Ala Met Ala Arg    170                 175                 180Asn Ser Gly Asp Gly Ser Gly Ser Gln Val Thr                185                 190

For position F61 (corresponding to the position in SEQ ID NO:1),hypersensitive mutations will include F61L or F61M. For position V81(corresponding to the position in SEQ ID NO:1), hypersensitive mutationswill include V81I or V81Y. For position I110 (corresponding to theposition in SEQ ID NO:1), hypersensitive mutations will include I110C orMOS. As some native PYR/PYL polypeptides have a valine at the positioncorresponding to I110 of SEQ ID NO:1, in some embodiments where positionI110 is mutated, the native amino acid will be valine, subsequentlymutated to C or S. For position E141 (corresponding to the position inSEQ ID NO:1), hypersensitive mutations will include E141C, E141I, E141L,E141M, E141N, E141T, E141V, E141W, or E141Y. For position A160(corresponding to the position in SEQ ID NO:1), hypersensitive mutationswill include A160C, A160I or A160V. As some native PYR/PYL polypeptideshave a valine at the position corresponding to A160 of SEQ ID NO:1, insome embodiments where position A160 is mutated, the native amino acidwill be valine, subsequently mutated to C or I.

Any of the mutations described herein can be made in any wildtypePYR/PYL polypeptide, for example, in the polypeptides of any of SEQ IDNOs:1-119 or in polypeptides substantially identical to any of SEQ IDNOs:1-119 or comprising any of SEQ ID NOs: 120-123. Analogous amino acidsubstitutions can be made, for example, in PYR/PYL receptors other thanPYR1 by aligning the PYR/PYL receptor polypeptide sequence to be mutatedwith the PYR1 receptor polypeptide sequence as set forth in SEQ ID NO:1.As a non-limiting example, an amino acid substitution in PYL2 that isanalogous to the amino acid substitution V81I in PYR1 as set forth inSEQ ID NO:1 can be determined by aligning the amino acid sequences ofPYL2 (SEQ ID NO:3) and PYR1 (SEQ ID NO:1) and identifying position V85in PYL2 as aligning with amino acid position V81 of PYR1 (SEQ ID NO:1).Analogous amino acid positions in PYR/PYL receptors are shown in FIGS. 2and 3. As an example, SEQ ID NOS:155-361 represent maize PYR/PYLpolypeptides containing the hypersensitive mutations described herein.It will be appreciated that the polypeptides can be further mutated(e.g., with conservative mutations, e.g., outside active sites) withoutsubstantially affecting activity. Accordingly, in some embodiments, thehypersensitive polypeptides as described herein comprise a sequencesubstantially (e.g., at least 70%, 75%, 80%, 85%, 90%, 95%, 98%)identical to the entire sequence of one of SEQ ID NOs: 155-361.

The extent to which one or more amino acid substitutions in the PYR/PYLreceptor activity renders the receptor hypersensitive to ABA can bequantitatively measured, for example by assaying phosphatase activity inthe presence of ABA and the PYR/PYL receptor comprising one or moreamino acid substitutions and comparing the phosphatase activity to thatof a control PYR/PYL receptor. A control PYR/PYL receptor will typicallybe the wildtype PYR/PYL polypeptide most similar to the mutated aPYR/PYL polypeptide. In some embodiments, e.g., when the startingprotein is not a wildtype PYR/PYL polypeptide, the control PYR/PYLpolypeptide can be substantially identical (e.g., at least 90, 95, or98% identical) to the test PYR/PYL polypeptide (i.e., suspected of beinghypersensitive) and having the wildtype amino acid at the correspondingposition. For example, if the mutant PYR/PYL receptor has a mutation ofF61X, where X is any non-F amino acid, the control would have F61 at thesame position but would otherwise be identical to the mutant PYR/PYLreceptor. If the mutant PYR/PYL receptor has a mutation of V81X, where Xis any non-V amino acid, the control would have V81 at the same positionbut would otherwise be identical to the mutant PYR/PYL receptor. If themutant PYR/PYL receptor has a mutation of I110X, where X is any non-I,non-V amino acid, the control would have I110 or V at the same positionbut would otherwise be identical to the mutant PYR/PYL receptor. If themutant PYR/PYL receptor has a mutation of E141X, where X is any non-Eamino acid, the control would have E141 at the same position but wouldotherwise be identical to the mutant PYR/PYL receptor. If the mutantPYR/PYL receptor has a mutation of A160X, where X is any non-A, non-Vamino acid, the control would have A160 or valine at the same positionbut would otherwise be identical to the mutant PYR/PYL receptor.

In some embodiments, a mutated PYR/PYL receptor polypeptide comprisestwo or more amino acid substitutions as described herein. In someembodiments, the two or more amino acid substitutions corresponding to,F61X, V81X, I110X, E141X, and A160X, in PYR1 as set forth in SEQ IDNO:1, where X is the amino acid indicated herein as resulting inhypersensitivity.

Embodiments of the present invention provide for use of the aboveproteins and/or nucleic acid sequences, encoding such polypeptides, inthe methods and compositions (e.g., expression cassettes, transgenicplants, plants with in situ PYR/PYL modifications, etc.) of the presentinvention. The isolation of a polynucleotide sequence encoding a plantwild-type PYR/PYL receptor (e.g., from plants where PYR/PYL sequenceshave not yet been identified) may be accomplished by a number oftechniques. For instance, oligonucleotide probes based on the PYR/PYLcoding sequences disclosed (e.g., as listed in the SEQUENCE LISTING)here can be used to identify the desired wild-type PYR/PYL gene in acDNA or genomic DNA library. To construct genomic libraries, largesegments of genomic DNA are generated by random fragmentation, e.g.,using restriction endonucleases, and are ligated with vector DNA to formconcatemers that can be packaged into the appropriate vector. To preparea cDNA library, mRNA is isolated from the desired tissue, such as a leaffrom a particular plant species, and a cDNA library containing the genetranscript of interest is prepared from the mRNA. Alternatively, cDNAmay be prepared from mRNA extracted from other tissues in which PYR/PYLgene is expressed.

The cDNA or genomic library can then be screened using a probe basedupon the sequence of a PYR/PYL gene disclosed here. Probes may be usedto hybridize with genomic DNA or cDNA sequences to isolate homologousgenes in the same or different plant species. Alternatively, antibodiesraised against a polypeptide can be used to screen an mRNA expressionlibrary.

Alternatively, the nucleic acids encoding PYR/PYL can be amplified fromnucleic acid samples using amplification techniques. For instance,polymerase chain reaction (PCR) technology can be used to amplify thecoding sequences of PYR/PYL directly from genomic DNA, from cDNA, fromgenomic libraries or cDNA libraries. PCR and other in vitroamplification methods may also be useful, for example, to clonepolynucleotide sequences encoding PYR/PYL to be expressed, to makenucleic acids to use as probes for detecting the presence of the desiredmRNA in samples, for nucleic acid sequencing, or for other purposes. Fora general overview of PCR see PCR Protocols: A Guide to Methods andApplications (Innis, M., Gelfand, D., Sninsky, J. and White, T., eds.),Academic Press, San Diego (1990). Appropriate primers and probes foridentifying sequences from plant tissues are generated from comparisonsof the sequences provided here with other related genes.

In some embodiments, the partial or entire genome of a number of plantshas been sequenced and open reading frames identified. By a BLASTsearch, one can identify the coding sequence for wild-type PYR/PYL invarious plants.

III. Methods of Making Hypersensitive PYR/PYL Receptor Polypeptides

In another aspect, the present invention provides for methods of makingABA hypersensitive PYR/PYL receptor polypeptides comprising one or moreamino acid substitutions. In some embodiments, the method comprisesmutagenizing a wild-type PYR/PYL receptor and determining whether themutagenized PYR/PYL receptor is hypersensitive to ABA.

Mutated PYR/PYL receptor polypeptides can be constructed by mutating theDNA sequences that encode the corresponding wild-type PYR/PYL receptorpolypeptide (e.g., a wild-type PYR/PYL polypeptide of any of SEQ IDNOs:1-119, having any of SEQ ID NO:s 120-123, or a corresponding variantfrom which the mutant PYR/PYL receptor polypeptide of the invention isderived), such as by using site-directed or random mutagenesis. Nucleicacid molecules encoding the wild-type PYR/PYL receptor polypeptide canbe mutated by a variety of polymerase chain reaction (PCR) techniqueswell-known to one of ordinary skill in the art. (See, e.g., PCRStrategies (M. A. Innis, D. H. Gelfand, and J. J. Sninsky eds., 1995,Academic Press, San Diego, Calif.) at Chapter 14; PCR Protocols: A Guideto Methods and Applications (M. A. Innis, D. H. Gelfand, J. J. Sninsky,and T. J. White eds., Academic Press, N Y, 1990).

As a non-limiting example, mutagenesis may be accomplished usingsite-directed mutagenesis, in which point mutations, insertions, ordeletions are made to a DNA template. Kits for site-directed mutagenesisare commercially available, such as the QuikChange Site-DirectedMutagenesis Kit (Stratagene). Briefly, a DNA template to be mutagenizedis amplified by PCR according to the manufacturer's instructions using ahigh-fidelity DNA polymerase (e.g., Pfu Turbo™) and oligonucleotideprimers containing the desired mutation. Incorporation of theoligonucleotides generates a mutated plasmid, which can then betransformed into suitable cells (e.g., bacterial or yeast cells) forsubsequent screening to confirm mutagenesis of the DNA.

As another non-limiting example, mutagenesis may be accomplished bymeans of error-prone PCR amplification (ePCR), which modifies PCRreaction conditions (e.g., using error-prone polymerases, varyingmagnesium or manganese concentration, or providing unbalanced dNTPratios) in order to promote increased rates of error in DNA replication.Kits for ePCR mutagenesis are commercially available, such as theGeneMorph® PCR Mutagenesis kit (Stratagene) and Diversify® PCR RandomMutagenesis Kit (Clontech). Briefly, DNA polymerase (e.g., Taqpolymerase), salt (e.g., MgCl2, MgSO4, or MnSO4), dNTPs in unbalancedratios, reaction buffer, and DNA template are combined and subjected tostandard PCR amplification according to manufacturer's instructions.Following ePCR amplification, the reaction products are cloned into asuitable vector to construct a mutagenized library, which can then betransformed into suitable cells (e.g., yeast cells) for subsequentscreening (e.g., via a two-hybrid screen) as described below.

Alternatively, mutagenesis can be accomplished by recombination (i.e.DNA shuffling). Briefly, a shuffled mutant library is generated throughDNA shuffling using in vitro homologous recombination by randomfragmentation of a parent DNA followed by reassembly using PCR,resulting in randomly introduced point mutations. Methods of performingDNA shuffling are known in the art (see, e.g., Stebel, S. C. et al.,Methods Mol Biol 352:167-190 (2007)).

Optionally, multiple rounds of mutagenesis may be performed in order toimprove the efficiency of mutant proteins isolated. Thus, in someembodiments, PYR/PYL mutants isolated from ePCR and subsequent screeningmay be pooled and used as templates for later rounds of mutagenesis.

In some embodiments, the variants are generated by exposing a plant ofplant seeds or cells to a mutagen selecting the plant or cell carrying ahypersensitive PYR/PYL polypeptide as described herein by phenotype orgenotype. Examples of mutagens include, e.g., chemical mutagens (e.g.,EMS) or radiological mutagens. Variants having a desired mutation can beselected based on phenotype of genotype (e.g., by using TILLINGtechniques).

In some embodiments, the method comprises mutagenizing a wild-typePYR/PYL receptor in situ and determining whether the mutagenized PYR/PYLreceptor is hypersensitive to ABA. Mutated PYR/PYL receptor polypeptidescan be constructed by mutating the DNA sequences that encode thecorresponding wild-type PYR/PYL receptor polypeptide (e.g., a wild-typePYR/PYL polypeptide of any of SEQ ID NOs:1-119, having any of SEQ IDNO:s 120-123, or a corresponding variant from which the mutant PYR/PYLreceptor polypeptide of the invention is derived), such as by usingsite-directed or random mutagenesis.

IV. Screening for Hypersensitive PYR/PYL Receptor Polypeptides

The hypersensitivity of the mutant PYR/PYL receptors described hereincan be measured in several alternative ways. When expressed in yeast,most wild-type PYR/PYL receptors will only bind to the type 2 proteinphosphatase (PP2C) HAB1 (or other PP2Cs) when the appropriate yeastcells are grown in the presence of ABA. Thus, in some embodiments,hypersensitivity can be measured by determining the ability of a PYR/PYLmutant receptor, expressed in yeast, to bind to and inactivate PP2C inyeast to a greater extent than a control PYR/PYL receptor expressed inyeast. In some embodiments, the hypersensitive mutant PYR/PYL receptorcomprises mutations that result in the mutated receptor inhibiting theactivity of the PP2C in a phosphatase assay in the presence of ABA atleast about 10%, at least about 20%, at least about 30%, at least about40%, at least about 50%, at least about 60%, at least about 70%, atleast about 80% or more as compared to a wild-type or other controlPYR/PYL receptor in the presence of the same concentration of ABA.Several test concentrations ranging from low nM to low μM could beconducted to infer IC₅₀ values and the IC₅₀ values of hypersensitivemutants are substantially lower than appropriate wild type controls.

Alternatively, cell-based or plant-based methods of screening can beused. For example, cells that naturally express a wild-type PYR/PYLreceptor polypeptide or that recombinantly express a wild-type ormutated PYR/PYL receptor polypeptide can be used. In some embodiments,the cells used are plant cells, animal cells, bacterial cells, fungalcells, including but not limited to yeast cells, insect cells, ormammalian cells. In general terms, the screening methods involvecomparing the activity of a mutated PYR/PYL receptor polypeptide to theactivity of a wild-type PYR/PYL receptor polypeptide in the presence ofABA, e.g., by comparing ABA-regulated gene expression in the wild-typeand mutant PYR/PYL receptor-expressing cells or plants.

One exemplary assay involves testing whether a mutated PYR/PYL receptorcan bind to a type 2 protein phosphatase (PP2C) (e.g., Homology to ABI1(HAB1)) in the presence of ABA. Binding assays can involve contacting amutated PYR/PY1 receptor polypeptide with a PP2C and allowing sufficienttime for the PYR/PYL receptor and PP2C to form a binding complex. Anybinding complexes formed can be detected using any of a number ofestablished analytical techniques. Protein binding assays include, butare not limited to, methods that measure co-precipitation orco-migration on non-denaturing SDS-polyacrylamide gels, and co-migrationon Western blots (see, e.g., Bennet, J. P. and Yamamura, H. I. (1985)“Neurotransmitter, Hormone or Drug Receptor Binding Methods,” inNeurotransmitter Receptor Binding (Yamamura, H. I., et al., eds.), pp.61-89. Other binding assays involve the use of mass spectrometry or NMRtechniques to identify molecules bound to the PYR/PYL polypeptide. ThePYR/PYL polypeptide protein utilized in such assays can be naturallyexpressed, cloned or synthesized.

In some embodiments, mammalian or yeast two-hybrid approaches (see,e.g., Bartel, P. L. et. al. Methods Enzymol, 254:241 (1995)) can be usedto identify polypeptides or other molecules that interact or bind whenexpressed together in a cell. In some embodiments, a hypersensitivePYR/PYL polypeptide is identified in a two-hybrid assay between aPYR/PYL polypeptide and a PP2C polypeptide, wherein the PYR/PYLpolypeptide and the PP2C bind in the presence of ABA.

In another exemplary assay, the level of basal activity of a mutatedPYR/PYL receptor polypeptide (i.e., level of activity in the absence ofABA) can be determined using an enzymatic phosphatase assay, in whichthe PYR/PYL receptor and PP2C are incubated in the presence of ABA. Inthis type of assay, a decrease in phosphatase activity in the presenceof ABA to a greater extent than occurred for a control PYR/PYL receptoris indicative of hypersensitive PYR/PYL receptor. A decrease inphosphatase activity can be determined and quantified using anydetection reagent known in the art, e.g., a colorimetric detectionreagent such as para-nitrophenylphosphate.

Hypersensitive PYR/PYL receptor polypeptides that are initiallyidentified by any of the foregoing screening methods can be furthertested to validate the apparent activity and/or determine otherbiological effects of the hypersensitive PYR/PYL receptor polypeptide.In some cases, the PYR/PYL receptor polypeptide is tested for theability to affect plant stress (e.g., drought tolerance and/or high salttolerance), seed germination, or another phenotype affected by ABA. Anumber of such assays and phenotypes are known in the art and can beemployed according to the methods of the invention.

V. Recombinant Expression Vectors

Once a polynucleotide encoding a mutated PYR/PYL receptor polypeptide isobtained, it can also be used to prepare an expression cassette forexpressing the mutated PYR/PYL receptor polypeptide in a transgenicplant, directed by a heterologous promoter. Increased expression ofmutated PYR/PYL polynucleotide is useful, for example, to produce plantsthat selectively activate PYR/PYL receptors, thus enhancing stresstolerance.

Any of a number of means well known in the art can be used to drivemutated PYR/PYL activity or expression in plants. Any organ can betargeted, such as shoot vegetative organs/structures (e.g. leaves, stemsand tubers), roots, flowers and floral organs/structures (e.g. bracts,sepals, petals, stamens, carpels, anthers and ovules), seed (includingembryo, endosperm, and seed coat) and fruit. Alternatively, the mutatedPYR/PYL polynucleotide can be expressed specifically in certain celland/or tissue types within one or more organs (e.g., guard cells inleaves using a guard cell-specific promoter). Alternatively, the mutatedPYR/PYL polynucleotide can be expressed constitutively (e.g., using theCaMV 35S promoter).

To use a polynucleotide sequence for a mutated PYR/PYL receptorpolypeptide in the above techniques, recombinant DNA vectors suitablefor transformation of plant cells are prepared. Techniques fortransforming a wide variety of higher plant species are well known anddescribed in the technical and scientific literature. See, e.g., Weisinget al. Ann. Rev. Genet. 22:421-477 (1988). A DNA sequence coding for themutated PYR/PYL receptor polypeptide preferably will be combined withtranscriptional and translational initiation regulatory sequences whichwill direct the transcription of the sequence from the gene in theintended tissues of the transformed plant.

For example, a plant promoter fragment may be employed to directexpression of the mutated PYR/PYL polynucleotide in all tissues of aregenerated plant. Such promoters are referred to herein as“constitutive” promoters and are active under most environmentalconditions and states of development or cell differentiation. Examplesof constitutive promoters include the cauliflower mosaic virus (CaMV)35S transcription initiation region, the 1′- or 2′-promoter derived fromT-DNA of Agrobacterium tumafaciens, and other transcription initiationregions from various plant genes known to those of skill.

Alternatively, the plant promoter may direct expression of the mutatedPYR/PYL receptor protein in a specific tissue (tissue-specificpromoters) or may be otherwise under more precise environmental control(inducible promoters). Examples of tissue-specific promoters underdevelopmental control include promoters that initiate transcription onlyin certain tissues, such as leaves or guard cells (including but notlimited to those described in WO 2005/085449; U.S. Pat. No. 6,653,535;Li et al., Sci China C Life Sci. 2005 April; 48(2):181-6; Husebye, etal., Plant Physiol, April 2002, Vol. 128, pp. 1180-1188; and Plesch, etal., Gene, Volume 249, Number 1, 16 May 2000, pp. 83-89(7)). Examples ofenvironmental conditions that may affect transcription by induciblepromoters include anaerobic conditions, elevated temperature, or thepresence of light.

If proper protein expression is desired, a polyadenylation region at the3′-end of the coding region should be included. The polyadenylationregion can be derived from a naturally occurring PYR/PYL gene, from avariety of other plant genes, or from T-DNA.

The vector comprising the sequences (e.g., promoters or PYR/PYL codingregions) will typically comprise a marker gene that confers a selectablephenotype on plant cells. For example, the marker may encode biocideresistance, particularly antibiotic resistance, such as resistance tokanamycin, G418, bleomycin, hygromycin, or herbicide resistance, such asresistance to chlorosluforon or Basta.

In some embodiments, the mutated PYR/PYL nucleic acid sequence isexpressed recombinantly in plant cells. A variety of differentexpression constructs, such as expression cassettes and vectors suitablefor transformation of plant cells, can be prepared. Techniques fortransforming a wide variety of higher plant species are well known anddescribed in the technical and scientific literature. See, e.g., Weisinget al. Ann. Rev. Genet. 22:421-477 (1988). A DNA sequence coding for aPYR/PYL protein can be combined with cis-acting (promoter) andtransacting (enhancer) transcriptional regulatory sequences to directthe timing, tissue type and levels of transcription in the intendedtissues of the transformed plant. Translational control elements canalso be used.

Embodiments of the present invention also provide for a mutated PYR/PYLnucleic acid operably linked to a promoter which, in some embodiments,is capable of driving the transcription of the PYR/PYL coding sequencein plants. The promoter can be, e.g., derived from plant or viralsources. The promoter can be, e.g., constitutively active, inducible, ortissue specific. In construction of recombinant expression cassettes,vectors, transgenics, of the invention, a different promoters can bechosen and employed to differentially direct gene expression, e.g., insome or all tissues of a plant or animal.

Constitutive Promoters

A fragment can be employed to direct expression of a mutated PYR/PYLnucleic acid in all transformed cells or tissues, e.g., as those of aregenerated plant. The term “constitutive regulatory element” means aregulatory element that confers a level of expression upon anoperatively linked nucleic molecule that is relatively independent ofthe cell or tissue type in which the constitutive regulatory element isexpressed. A constitutive regulatory element that is expressed in aplant generally is widely expressed in a large number of cell and tissuetypes. Promoters that drive expression continuously under physiologicalconditions are referred to as “constitutive” promoters and are activeunder most environmental conditions and states of development or celldifferentiation.

A variety of constitutive regulatory elements useful for ectopicexpression in a transgenic plant are well known in the art. Thecauliflower mosaic virus 35S (CaMV 35S) promoter, for example, is awell-characterized constitutive regulatory element that produces a highlevel of expression in all plant tissues (Odell et al., Nature313:810-812 (1985)). The CaMV 35S promoter can be particularly usefuldue to its activity in numerous diverse plant species (Benfey and Chua,Science 250:959-966 (1990); Futterer et al., Physiol. Plant 79:154(1990); Odell et al., supra, 1985). A tandem 35S promoter, in which theintrinsic promoter element has been duplicated, confers higherexpression levels in comparison to the unmodified 35S promoter (Kay etal., Science 236:1299 (1987)). Other useful constitutive regulatoryelements include, for example, the cauliflower mosaic virus 19Spromoter; the Figwort mosaic virus promoter; and the nopaline synthase(nos) gene promoter (Singer et al., Plant Mol. Biol. 14:433 (1990); An,Plant Physiol. 81:86 (1986)).

Additional constitutive regulatory elements including those forefficient expression in monocots also are known in the art, for example,the pEmu promoter and promoters based on the rice Actin-1 5′ region(Last et al., Theor. Appl. Genet. 81:581 (1991); Mcelroy et al., Mol.Gen. Genet. 231:150 (1991); Mcelroy et al., Plant Cell 2:163 (1990)).Chimeric regulatory elements, which combine elements from differentgenes, also can be useful for ectopically expressing a nucleic acidmolecule encoding a mutated PYR/PYL receptor protein (Comai et al.,Plant Mol. Biol. 15:373 (1990)).

Other examples of constitutive promoters include the 1′- or 2′-promoterderived from T-DNA of Agrobacterium tumafaciens (see, e.g., Mengiste(1997) supra; O'Grady (1995) Plant Mol. Biol. 29:99-108); actinpromoters, such as the Arabidopsis actin gene promoter (see, e.g., Huang(1997) Plant Mol. Biol. 1997 33:125-139); alcohol dehydrogenase (Adh)gene promoters (see, e.g., Millar (1996) Plant Mol. Biol. 31:897-904);ACT11 from Arabidopsis (Huang et al. Plant Mol. Biol. 33:125-139(1996)), Cat3 from Arabidopsis (GenBank No. U43147, Zhong et al., Mol.Gen. Genet. 251:196-203 (1996)), the gene encoding stearoyl-acyl carrierprotein desaturase from Brassica napus (Genbank No. X74782, Solocombe etal. Plant Physiol. 104:1167-1176 (1994)), GPc1 from maize (GenBank No.X15596, Martinez et al. J. Mol. Biol 208:551-565 (1989)), Gpc2 frommaize (GenBank No. U45855, Manjunath et al., Plant Mol. Biol. 33:97-112(1997)), other transcription initiation regions from various plant genesknown to those of skill. See also Holtorf Plant Mol. Biol. 29:637-646(1995).

Inducible Promoters

Alternatively, a plant promoter may direct expression of the mutatedPYR/PYL polynucleotide under the influence of changing environmentalconditions or developmental conditions. Examples of environmentalconditions that may affect transcription by inducible promoters includeanaerobic conditions, elevated temperature, drought, or the presence oflight. Such promoters are referred to herein as “inducible” promoters.In some embodiments, an inducible promoter is one that is induced by oneor more environmental stressors, including but not limited to, drought,freezing cold, and high salt. For example, the invention can incorporatea drought-specific promoter such as a drought-inducible promoter ofmaize (e.g., the maize rab17 drought-inducible promoter (Vilardell etal. (1991) Plant Mol. Biol. 17:985-993; Vilardell et al. (1994) PlantMol. Biol. 24:561-569)); or alternatively a cold, drought, and high saltinducible promoter from potato (Kirch (1997) Plant Mol. Biol.33:897-909) or from Arabidopsis (e.g., the rd29A promoter (Kasuga et al.(1999) Nature Biotechnology 17:287-291). Other environmentalstress-inducible promoters include promoters from the following genes:Rab21, Wsi18, Lea3, Uge1, Dip1, and R1G1B in rice (Yi et al. (2010)Planta 232:743-754).

In some embodiments, a plant promoter is a stress-inducible promoter(e.g., a drought-, cold-, or salt-inducible promoter) that comprises adehydration-responsive element (DRE) and/or an ABA-responsive element(ABRE), including but not limited to the rd29A promoter.

Alternatively, plant promoters which are inducible upon exposure toplant hormones, such as auxins, are used to express the mutated PYR/PYLpolynucleotide. For example, the invention can use the auxin-responseelements E1 promoter fragment (AuxREs) in the soybean (Glycine max L.)(Liu (1997) Plant Physiol. 115:397-407); the auxin-responsiveArabidopsis GST6 promoter (also responsive to salicylic acid andhydrogen peroxide) (Chen (1996) Plant J. 10: 955-966); theauxin-inducible parC promoter from tobacco (Sakai (1996) 37:906-913); aplant biotin response element (Streit (1997) Mol. Plant MicrobeInteract. 10:933-937); and, the promoter responsive to the stresshormone abscisic acid (Sheen (1996) Science 274:1900-1902).

Plant promoters inducible upon exposure to chemicals reagents that maybe applied to the plant, such as herbicides or antibiotics, are alsouseful for expressing the mutated PYR/PYL polynucleotide. For example,the maize In2-2 promoter, activated by benzenesulfonamide herbicidesafeners, can be used (De Veylder (1997) Plant Cell Physiol.38:568-577); application of different herbicide safeners inducesdistinct gene expression patterns, including expression in the root,hydathodes, and the shoot apical meristem. A PYR/PYL coding sequence canalso be under the control of, e.g., a tetracycline-inducible promoter,e.g., as described with transgenic tobacco plants containing the Avenasativa L. (oat) arginine decarboxylase gene (Masgrau (1997) Plant J.11:465-473); or, a salicylic acid-responsive element (Stange (1997)Plant J. 11:1315-1324; Uknes et al., Plant Cell 5:159-169 (1993); Bi etal., Plant J. 8:235-245 (1995)).

Examples of useful inducible regulatory elements includecopper-inducible regulatory elements (Mett et al., Proc. Natl. Acad.Sci. USA 90:4567-4571 (1993); Furst et al., Cell 55:705-717 (1988));tetracycline and chlor-tetracycline-inducible regulatory elements (Gatzet al., Plant J. 2:397-404 (1992); Röder et al., Mol. Gen. Genet.243:32-38 (1994); Gatz, Meth. Cell Biol. 50:411-424 (1995)); ecdysoneinducible regulatory elements (Christopherson et al., Proc. Natl. Acad.Sci. USA 89:6314-6318 (1992); Kreutzweiser et al., Ecotoxicol. Environ.Safety 28:14-24 (1994)); heat shock inducible regulatory elements(Takahashi et al., Plant Physiol. 99:383-390 (1992); Yabe et al., PlantCell Physiol. 35:1207-1219 (1994); Ueda et al., Mol. Gen. Genet.250:533-539 (1996)); and lac operon elements, which are used incombination with a constitutively expressed lac repressor to confer, forexample, IPTG-inducible expression (Wilde et al., EMBO J. 11:1251-1259(1992)). An inducible regulatory element useful in the transgenic plantsof the invention also can be, for example, a nitrate-inducible promoterderived from the spinach nitrite reductase gene (Back et al., Plant Mol.Biol. 17:9 (1991)) or a light-inducible promoter, such as thatassociated with the small subunit of RuBP carboxylase or the LHCP genefamilies (Feinbaum et al., Mol. Gen. Genet. 226:449 (1991); Lam andChua, Science 248:471 (1990)).

Tissue-Specific Promoters

Alternatively, the plant promoter may direct expression of the mutatedPYR/PYL polynucleotide in a specific tissue (tissue-specific promoters).Tissue specific promoters are transcriptional control elements that areonly active in particular cells or tissues at specific times duringplant development, such as in vegetative tissues or reproductivetissues.

Examples of tissue-specific promoters under developmental controlinclude promoters that initiate transcription only (or primarily only)in certain tissues, such as vegetative tissues, e.g., roots or leaves,or reproductive tissues, such as fruit, ovules, seeds, pollen, pistols,flowers, or any embryonic tissue, or epidermis or mesophyll.Reproductive tissue-specific promoters may be, e.g., ovule-specific,embryo-specific, endosperm-specific, integument-specific, seed and seedcoat-specific, pollen-specific, petal-specific, sepal-specific, or somecombination thereof. In some embodiments, the promoter is cell-typespecific, e.g., guard cell-specific.

Epidermal-specific promoters include, for example, the Arabidopsis LTP1promoter (Thoma et al. (1994) Plant Physiol. 105(1):35-45), the CER1promoter (Aarts et al. (1995) Plant Cell 7:2115-27), and the CER6promoter (Hooker et al. (2002) Plant Physiol 129:1568-80), and theorthologous tomato LeCER6 (Vogg et al. (2004) J. Exp Bot. 55:1401-10).

Guard cell-specific promoters include, for example, the DGP1 promoter(Li et al. (2005) Science China C Life Sci. 48:181-186).

Other tissue-specific promoters include seed promoters. Suitableseed-specific promoters are derived from the following genes: MAC1 frommaize (Sheridan (1996) Genetics 142:1009-1020); Cat3 from maize (GenBankNo. L05934, Abler (1993) Plant Mol. Biol. 22:10131-1038); vivparous-1from Arabidopsis (Genbank No. U93215); atmyc1 from Arabidopsis (Urao(1996) Plant Mol. Biol. 32:571-57; Conceicao (1994) Plant 5:493-505);napA from Brassica napus (GenBank No. J02798, Josefsson (1987) JBL26:12196-1301); and the napin gene family from Brassica napus (Sjodahl(1995) Planta 197:264-271).

A variety of promoters specifically active in vegetative tissues, suchas leaves, stems, roots and tubers, can also be used to expresspolynucleotides encoding mutated PYR/PYL receptor polypeptides. Forexample, promoters controlling patatin, the major storage protein of thepotato tuber, can be used, see, e.g., Kim (1994) Plant Mol. Biol.26:603-615; Martin (1997) Plant J. 11:53-62. The ORF13 promoter fromAgrobacterium rhizogenes that exhibits high activity in roots can alsobe used (Hansen (1997) Mol. Gen. Genet. 254:337-343. Other usefulvegetative tissue-specific promoters include: the tarin promoter of thegene encoding a globulin from a major taro (Colocasia esculenta L.Schott) corm protein family, tarin (Bezerra (1995) Plant Mol. Biol.28:137-144); the curculin promoter active during taro corm development(de Castro (1992) Plant Cell 4:1549-1559) and the promoter for thetobacco root-specific gene TobRB7, whose expression is localized to rootmeristem and immature central cylinder regions (Yamamoto (1991) PlantCell 3:371-382).

Leaf-specific promoters, such as the ribulose biphosphate carboxylase(RBCS) promoters, can also be used. For example, the tomato RBCS1, RBCS2and RBCS3A genes are expressed in leaves and light-grown seedlings, onlyRBCS1 and RBCS2 are expressed in developing tomato fruits (Meier (1997)FEBS Lett. 415:91-95). A ribulose bisphosphate carboxylase promotersexpressed almost exclusively in mesophyll cells in leaf blades and leafsheaths at high levels, described by Matsuoka (1994) Plant J. 6:311-319,can be used. Another leaf-specific promoter is the light harvestingchlorophyll a/b binding protein gene promoter, see, e.g., Shiina (1997)Plant Physiol. 115:477-483; Casal (1998) Plant Physiol. 116:1533-1538.The Arabidopsis thaliana myb-related gene promoter (Atmyb5) described byLi (1996) FEBS Lett. 379:117-121, is leaf-specific. The Atmyb5 promoteris expressed in developing leaf trichomes, stipules, and epidermal cellson the margins of young rosette and cauline leaves, and in immatureseeds. Atmyb5 mRNA appears between fertilization and the 16 cell stageof embryo development and persists beyond the heart stage. A leafpromoter identified in maize by Busk (1997) Plant J. 11:1285-1295, canalso be used.

Another class of useful vegetative tissue-specific promoters aremeristematic (root tip and shoot apex) promoters. For example, the“SHOOTMERISTEMLESS” and “SCARECROW” promoters, which are active in thedeveloping shoot or root apical meristems, described by Di Laurenzio(1996) Cell 86:423-433; and, Long (1996) Nature 379:66-69; can be used.Another useful promoter is that which controls the expression of3-hydroxy-3-methylglutaryl coenzyme A reductase HMG2 gene, whoseexpression is restricted to meristematic and floral (secretory zone ofthe stigma, mature pollen grains, gynoecium vascular tissue, andfertilized ovules) tissues (see, e.g., Enjuto (1995) Plant Cell.7:517-527). Also useful are kn1-related genes from maize and otherspecies which show meristem-specific expression, see, e.g., Granger(1996) Plant Mol. Biol. 31:373-378; Kerstetter (1994) Plant Cell6:1877-1887; Hake (1995) Philos. Trans. R. Soc. Lond. B. Biol. Sci.350:45-51. For example, the Arabidopsis thaliana KNAT1 promoter (see,e.g., Lincoln (1994) Plant Cell 6:1859-1876).

One of skill will recognize that a tissue-specific promoter may driveexpression of operably linked sequences in tissues other than the targettissue. Thus, as used herein a tissue-specific promoter is one thatdrives expression preferentially in the target tissue, but may also leadto some expression in other tissues as well.

In another embodiment, the mutated PYR/PYL polynucleotide is expressedthrough a transposable element. This allows for constitutive, yetperiodic and infrequent expression of the constitutively activepolypeptide. The invention also provides for use of tissue-specificpromoters derived from viruses including, e.g., the tobamovirussubgenomic promoter (Kumagai (1995) Proc. Natl. Acad. Sci. USA92:1679-1683; the rice tungro bacilliform virus (RTBV), which replicatesonly in phloem cells in infected rice plants, with its promoter whichdrives strong phloem-specific reporter gene expression; the cassava veinmosaic virus (CVMV) promoter, with highest activity in vascularelements, in leaf mesophyll cells, and in root tips (Verdaguer (1996)Plant Mol. Biol. 31:1129-1139).

VI. Production of Plants Comprising Hypersensitive Mutations

In another aspect, the present invention provides for transgenic plantscomprising recombinant expression cassettes for expressing ahypersensitive PYR/PYL receptor protein as described herein in a plant.In some embodiments, a transgenic plant is generated that contains acomplete or partial sequence of a polynucleotide that is derived from aspecies other than the species of the transgenic plant. It should berecognized that transgenic plants encompass the plant or plant cell inwhich the expression cassette is introduced as well as progeny of suchplants or plant cells that contain the expression cassette, includingthe progeny that have the expression cassette stably integrated in achromosome.

A recombinant expression vector comprising a PYR/PYL coding sequencedriven by a heterologous promoter may be introduced into the genome ofthe desired plant host by a variety of conventional techniques. Forexample, the DNA construct may be introduced directly into the genomicDNA of the plant cell using techniques such as electroporation andmicroinjection of plant cell protoplasts, or the DNA construct can beintroduced directly to plant tissue using ballistic methods, such as DNAparticle bombardment. Alternatively, the DNA construct may be combinedwith suitable T-DNA flanking regions and introduced into a conventionalAgrobacterium tumefaciens host vector. The virulence functions of theAgrobacterium tumefaciens host will direct the insertion of theconstruct and adjacent marker into the plant cell DNA when the cell isinfected by the bacteria. While transient expression of theconstitutively active PYR/PYL receptor is encompassed by the invention,generally expression of construction of the invention will be frominsertion of expression cassettes into the plant genome, e.g., such thatat least some plant offspring also contain the integrated expressioncassette.

Microinjection techniques are also useful for this purpose. Thesetechniques are well known in the art and thoroughly described in theliterature. The introduction of DNA constructs using polyethylene glycolprecipitation is described in Paszkowski et al. EMBO J. 3:2717-2722(1984). Electroporation techniques are described in Fromm et al. Proc.Natl. Acad. Sci. USA 82:5824 (1985). Ballistic transformation techniquesare described in Klein et al. Nature 327:70-73 (1987).

Agrobacterium tumefaciens-mediated transformation techniques, includingdisarming and use of binary vectors, are well described in thescientific literature. See, for example, Horsch et al. Science233:496-498 (1984), and Fraley et al. Proc. Natl. Acad. Sci. USA 80:4803(1983).

Transformed plant cells derived by any of the above transformationtechniques can be cultured to regenerate a whole plant that possessesthe transformed genotype and thus the desired phenotype such as enhancedabiotic stress resistance. Such regeneration techniques rely onmanipulation of certain phytohormones in a tissue culture growth medium,typically relying on a biocide and/or herbicide marker which has beenintroduced together with the desired nucleotide sequences. Plantregeneration from cultured protoplasts is described in Evans et al.,Protoplasts Isolation and Culture, Handbook of Plant Cell Culture, pp.124-176, MacMillilan Publishing Company, New York, 1983; and Binding,Regeneration of Plants, Plant Protoplasts, pp. 21-73, CRC Press, BocaRaton, 1985. Regeneration can also be obtained from plant callus,explants, organs, or parts thereof. Such regeneration techniques aredescribed generally in Klee et al. Ann. Rev. of Plant Phys. 38:467-486(1987).

One of skill will recognize that after the expression cassette is stablyincorporated in transgenic plants and confirmed to be operable, it canbe introduced into other plants by sexual crossing. Any of a number ofstandard breeding techniques can be used, depending upon the species tobe crossed.

The expression cassettes of the invention can be used to confer abioticstress resistance on essentially any plant. Thus, the invention has useover a broad range of plants, including species from the generaAsparagus, Atropa, Avena, Brassica, Citrus, Citrullus, Capsicum,Cucumis, Cucurbita, Daucus, Fragaria, Glycine, Gossypium, Helianthus,Heterocallis, Hordeum, Hyoscyamus, Lactuca, Linum, Lolium, Lycopersicon,Malus, Manihot, Majorana, Medicago, Nicotiana, Oryza, Panieum,Pannesetum, Persea, Pisum, Pyrus, Prunus, Raphanus, Secale, Senecio,Sinapis, Solanum, Sorghum, Trigonella, Triticum, Vitis, Vigna, and, Zea.In some embodiments, the plant is selected from the group consisting ofrice, maize, wheat, soybeans, cotton, canola, turfgrass, and alfalfa. Insome embodiments, the plant is an ornamental plant. In some embodiment,the plant is a vegetable- or fruit-producing plant.

Those of skill will recognize that a number of plant species can be usedas models to predict the phenotypic effects of transgene expression inother plants. For example, it is well recognized that both tobacco(Nicotiana) and Arabidopsis plants are useful models of transgeneexpression, particularly in other dicots.

In some embodiments, the plants of the invention have enhancedABA-mediated phenotypes, for example enhanced seed dormancy, as comparedto plants that are otherwise identical except for expression of thehypersensitive PYR/PYL receptor polypeptide. Those of skill in the artwill recognize that ABA is a well-studied plant hormone and that ABAmediates many changes in characteristics, any of which can be monitoredto determine changes in phenotype. In some embodiments, an enhancedABA-mediated phenotype is manifested by altered timing of seedgermination or altered stress (e.g., drought, freezing cold, and/orsalt) tolerance.

Abiotic stress resistance can be assayed according to any of a number ofwell-known techniques. For example, for drought tolerance, plants can begrown under conditions in which less than optimum water is provided tothe plant. Drought resistance can be determined by any of a number ofstandard measures including turgor pressure, growth, yield, and thelike. In some embodiments, a transgenic plant expressing a mutatedPYR/PYL receptor as described herein has enhanced drought tolerance ifthe loss of turgor in the transgenic plant is reduced by at least about10%, 15%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or more ascompared to a non-transgenic control plant over a defined period of time(e.g., over the course of 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 days ormore, e.g., 3, 4, 5 weeks or more).

In some embodiments, the enhanced ABA-mediated phenotype is enhancedtolerance to moderate or high salinity. Salinity tolerance can bedetermined by any of a number of standard measures, includinggermination, growth, yield, or plant survival, leaf injury, prematureloss of chlorophyll, and the like. In some embodiments, transgenicplants expressing a mutated PYR/PYL receptor as described herein haveenhanced salt tolerance if the survival of the transgenic plants undermoderate-salt or high-salt conditions (e.g., about 50 mM, 100 mM, 150mM, 200 mM, 250 mM, 300 mM NaCl or higher) is increased by at leastabout 10%, 15%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or more ascompared to a non-transgenic control plant over a defined period of time(e.g., over the course of 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 days ormore, e.g., 3, 4, 5 weeks or more).

Plant gene manipulations can now be precisely tailored in non-transgenicorganisms using the CRISPR/Cas9 genome editing method. In this bacterialantiviral and transcriptional regulatory system, a complex of two smallRNAs—the CRISPR-RNA (crRNA) and the transactivating crRNA(tracrRNA)—directs the nuclease (Cas9) to a specific DNA sequencecomplementary to the crRNA (Jinek, M., et al. Science 337, 816-821(2012)). Binding of these RNAs to Cas9 involves specific sequences andsecondary structures in the RNA. The two RNA components can besimplified into a single element, the single guide-RNA (sgRNA), which istranscribed from a cassette containing a target sequence defined by theuser (Jinek, M., et al. Science 337, 816-821 (2012)). This system hasbeen used for genome editing in humans, zebrafish, Drosophila, mice,nematodes, bacteria, yeast, and plants (Hsu, P. D., et al., Cell 157,1262-1278 (2014)). In this system the nuclease creates double strandedbreaks at the target region programmed by the sgRNA. These can berepaired by non-homologous recombination, which often yieldsinactivating mutations. The breaks can also be repaired by homologousrecombination, which enables the system to be used for gene targetedgene replacement (Li, J.-F., et al. Nat. Biotechnol. 31, 688-691, 2013;Shan, Q., et al. Nat. Biotechnol. 31, 686-688, 2013). The hypersensitivemutations described in this application can be introduced into plantsusing the CAS9/CRISPR system.

Accordingly, in some embodiments, instead of generating a transgenicplant, a native PYR/PYR coding sequence in a plant or plant cell can bealtered in situ to generate a plant or plant cell carrying apolynucleotide encoding a hypersensitive PYR/PYL polypeptide asdescribed herein. For example, in some embodiments, CRISPR technology isused to introduce one or more nucleotide changes into a PYR/PYL codingsequence in situ to change the appropriate codon to make a changecorresponding to F61X, V81X, I110X, or V163X of SEQ ID NO:1. TheCRISPR/Cas system has been modified for use in prokaryotic andeukaryotic systems for genome editing and transcriptional regulation.The “CRISPR/Cas” system refers to a widespread class of bacterialsystems for defense against foreign nucleic acid. CRISPR/Cas systems arefound in a wide range of eubacterial and archaeal organisms. CRISPR/Cassystems include type I, II, and III sub-types. Wild-type type IICRISPR/Cas systems utilize the RNA-mediated nuclease, Cas9 in complexwith guide and activating RNA to recognize and cleave foreign nucleicacid. Cas9 homologs are found in a wide variety of eubacteria,including, but not limited to bacteria of the following taxonomicgroups: Actinobacteria, Aquificae, Bacteroidetes-Chlorobi,Chlamydiae-Verrucomicrobia, Chlroflexi, Cyanobacteria, Firmicutes,Proteobacteria, Spirochaetes, and Thermotogae. An exemplary Cas9 proteinis the Streptococcus pyogenes Cas9 protein. Additional Cas9 proteins andhomologs thereof are described in, e.g., Chylinksi, et al., RNA Biol.2013 May 1; 10(5): 726-737; Nat. Rev. Microbiol. 2011 June; 9(6):467-477; Hou, et al., Proc Natl Acad Sci USA. 2013 Sep. 24;110(39):15644-9; Sampson et al., Nature. 2013 May 9; 497(7448):254-7;and Jinek, et al., Science. 2012 Aug. 17; 337(6096):816-21.

Accordingly, in one aspect, a method is provided of using CRISPR/CAS9 tointroduce at least one of the mutation described herein into a plantcell is performed. In some embodiments, a method of altering a (e.g.,native) nucleic acid encoding PYR/PYL polypeptide in a plant isprovided. In some embodiments, the method comprises introducing into theplant cell containing and expressing a DNA molecule having a targetnucleic acid encoding PYR/PYL polypeptide an engineered, non-naturallyoccurring Clustered Regularly Interspaced Short Palindromic Repeats(CRISPR)-CRISPR associated (Cas) (CRISPR-Cas) system. In someembodiments, the CRISPR-Cas system comprises one or more vectorscomprising: a) a first regulatory element operable in a plant celloperably linked to at least one nucleotide sequence encoding aCRISPR-Cas system guide RNA that hybridizes with the target sequence,and b) a second regulatory element operable in a plant cell operablylinked to a nucleotide sequence encoding a Type-II Cas9 protein, whereincomponents (a) and (b) are located on same or different vectors of thesystem, whereby the guide RNA targets the target sequence and the Cas9protein cleaves the DNA molecule, whereby at least one of thehypersensitive mutations described herein is introduced into the targetnucleic acid encoding the PYR/PYL polypeptide. In some embodiments, thePRY/PYL polypeptide is selected from any of SEQ ID NO:1, 2, 3, 4, 5, 6,7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43,44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61,62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79,80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97,98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112,113, 114, 115, 116, 117, 118, or 119 or a substantially identicalpolypeptide. In some embodiments, the plant is from a genus selectedfrom Asparagus, Atropa, Avena, Brassica, Citrus, Citrullus, Capsicum,Cucumis, Cucurbita, Daucus, Fragaria, Glycine, Gossypium, Helianthus,Heterocallis, Hordeum, Hyoscyamus, Lactuca, Linum, Lolium, Lycopersicon,Malta, Manihot, Majorana, Medicago, Nicotiana, Oryza, Panieum,Pannesetum, Persea, Pisum, Pyrus, Prunus, Raphanus, Secale, Senecio,Sinapis, Solanum, Sorghum, Trigonella, Triticum, Vitis, Vigna, and, Zea.In some embodiments, the plant is selected from the group consisting ofrice, maize, wheat, and soybean. In some embodiments, the hypersensitivemutation introduced to the target nucleic acid is (corresponding totheir position in Arabidopsis PYR1 (SEQ ID NO:1)): F61, V81, I110, E141,or A160 or a combination thereof. In some embodiments, no othermutations are introduced into the target nucleic acid. Also provided asa plant or plant cell resulting from the above-described method. Such aplant will contain a non-naturally-occurring nucleic acid sequenceencoding the hypersensitive PYR/PYL polypeptide.

VII. PYR/PYL Fusion Proteins

In some embodiments, the hypersensitive PYR/PYL polypeptides describedherein are provided as fusion proteins, i.e., translational fusions withone or more fusion partner. In some embodiments, a hypersensitivePYR/PYL polypeptide is fused with a transcriptional activation ormodulation domain. A non-limiting example of such a domain is VP16 orVP64. The fusion proteins can further comprise a nuclear localizationsignal sequence such that the fusion protein, when translated in aeukaryotic host cell, is localized to the cell nucleus. Also providedare polynucleotides encoding such fusion proteins as well as host cellscomprising and expressing such polynucleotides. The polynucleotides insuch instances will be heterologous to the host cell, i.e., will not benaturally occurring, for example transformed into the cell.

Such fusion proteins are useful, for example, in controlling eukaryoticgene expression in the cell when co-expressed with a sequence-specificDNA binding domain fused with) ABA INSENSITIVE 1 (ABI1) or otherproteins having specific binding affinity for PYR/PYL proteins bindingABA. Exemplary sequence-specific DNA binding domains include, but arenot limited to zinc-finger proteins, TALENS, transcription factor DNAbinding domains, and RNA-guided DNA-binding domains of inactive Cas9(dCas9). When both fusion proteins are co-expressed in the cell in thepresence of ABA, the two fusion proteins will co-localized due to thebinding of ABA1 to the ABA-binding PYR/PYL protein, thereby bringing thetranscriptional activation or modulation domain in proximity to thetarget promoter, thereby regulating gene expression. Examples of systemsand their use in gene regulation, are described in, e.g., Konermann etal., Nature 500:472-476 (2013) and Liang et al., Science Vol. 4 Issue164 (2011).

RNA Directed Genome Modification

In one aspect provided herein is a method for introducing a mutation insitu at a PYR/PYL mutation target site in a plant cell genome, asdescribed herein. For example, in some embodiments, the PYR/PYL mutationtarget site comprises a nucleic acid that encodes for V89 of PYL-E orE149 of PYL. In certain embodiments the method comprises introducinginto the plant cell: 1) a CRISPR ribonucleic acid (crRNA) that includesa sequence substantially identical to SEQ ID NOS: 363, 364, 365, 366,367 or 369; 2) a transacting ribonucleic acid (tracRNA); 3) a nuclease(e.g., Cas9); and 4) a repair nucleic acid that can undergo homologousrecombination that contains the mutation. According to the subjectmethod, the crRNA and tracRNA directs the nuclease to the PYR/PYLmutation target site in a plant cell genome. Upon its recruitment, thenuclease (e.g., Cas9) creates a double strand break at the PYR/PYLmutation target site. The double strand break at the PYR/PYL mutationtarget site facilitates homologous recombination of the repair nucleicacid containing the mutation with a region of the plant cell genome thatincludes the PYR/PYL mutation target site, thereby introducing themutation at the PYR/PYL mutation target site.

Mutations can be introduced into any suitable plant cell using thesubject method. In some embodiments, the plant cell is a plant embryo.In certain embodiments, the plant cell is a maize plant cell.

Each component of the method can be introduced into the plant cell usingany suitable method known in the art. In certain embodiments, the crRNAand tracRNA are introduced into the cell as an expression cassettecontaining a polynucleotide (i.e., DNA) encoding the crRNA and/ortraRNA. In some embodiments, the expression cassette includes an RNApolymerase promoter operably linked to the polynucleotide encoding thecrRNA and/or traRNA, thereby allowing transcription of the crRNA and/ortraRNA. In some embodiments, the Cas9 is introduced into the cell as anexpression vector containing a promoter operably linked to apolynucleotide encoding Cas9. Any suitable promoter can be used,including but not limtied to, the promoters described herein. In certainembodiments, the promoter is a ubiquitin-1 promoter (e.g., prUbi-10).DNA construct (.e.g, the expression cassettes and vectors describedherein) can be introduced directly to plant tissue, for example, usingballistic methods, such as DNA particle bombardment.

Each of the crRNA, and the tracRNA, nuclease can be introducedseparately or together as part of one expression vector into the cell ofinterest (e.g., a maize plant cell). In certain embodiments, the crRNAand the tracRNA are fused together to create a guide ribonucleic acid(gRNA). In some embodiments, the gRNA includes, from 5′ to 3′, a crNAlinked to a tracRNA. In certain embodiments the crRNA, tracRNA, andnuclease (e.g., Cas9) are introduced together as nucleic acid cassettesincluded in one expression vector. Each component of the subject methodis discussed in detail below.

Guide RNA

In one aspect provided, provided herein is a guide RNA (gRNA) comprisinga CRISPR ribonucleic acid (crRNA) and a transacting RNA (tracRNA).

The crRNA of the subject gRNA comprises a nucleotide sequence that iscomplementary to a sequence in a PYR/PYL mutation target site andincludes a sequence that is substantially identical to SEQ ID NOS: 363,364, 365, 366, 367 or 369. In certain embodiments, the crRNA has asequence that is substantially identical to SEQ ID NOS: 363, 364, 365,366, 367 or 369. The subject crRNAs provided herein are particularlyuseful for creating mutations at a PYR/PYL mutation target site thatincludes a nucleic acid encoding for an amino acid corresponding to V89(SEQ ID NOS: 363, 364, 365, 366, 367) and E149 (SEQ ID NO:369) of PYL-E.As used herein, a “PYR/PYL mutation target site” refers to a region of apolynucleotide encoding for a PYR/PYL receptor that includes the sitewhere a mutation is introduced by the subject method. The crRNAinteracts with the PYR/PYL mutation target site in a sequence-specificmanner by hybridization to a sequence in the PYR/PYL mutation targetsite (e.g., the complementary strand of the PYR/PYL mutation targetsite) and, together with the tracRNA of the gRNA, recruits Cas9endonuclease to the PYR/PYL mutation target site. Cas9 endonucleaserecruited by the gRNA to the PYR/PYL mutation target site introduces adouble strand break in the PYR/PYL mutation target site. Any of themutations described herein can be made in any wildtype PYR/PYLpolypeptide. Analogous amino acid substitutions can be made, forexample, in PYR/PYL receptors other than PYL-E by aligning the PYR/PYLreceptor polypeptide sequence to be mutated with the PYL-E receptorpolypeptide sequence. Analogous amino acid positions in PYR/PYLrecetpros are shown in FIGS. 2 and 3.

In some embodiments, the PYR/PYL mutation target site has the sequenceof SEQ ID NO: 362, which includes a nucleic acid encoding for V89 ofPYL-E. In some embodiments, the PYR/PYL mutation target site has thesequence of SEQ ID NO:368, which includes a nucleic acid encoding forE149 of PYL-E.

In some embodiments, a crRNA has a length of 10 nucleotides (nt) to 100nucleotides (nt). In some embodiments, the crRNA has a length of 15, 16,17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 nt and includes asequence that is substantially identical to SEQ ID NOS: 362, 363, 364,365, 366 or 368. In some embodiments, the crRNA has a length of at least17 nt. In some embodiments, the crRNA has a length of 17 nt to 18 nt, 17nt to 19 nt, 17 nt to 20 nt, 17 nt to 21 nt, 17 nt to 22 nt, 17 nt to 23nt, 17 nt to 24 nt, 17 nt to 25 nt, 17 nt to 30 nt, 17 nt to 35 nt, 17nt to 40 nt, 17 nt to 45 nt, 17 nt to 50 nt, 17 nt to 55 nt, 17 nt to 60nt, 17 nt to 65 nt, 17 nt to 70 nt, 17 nt to 75 nt, 17 nt to 80 nt, 17nt to 85 nt, 17 nt to 90 nt, 17 nt to 95 nt, or 17 nt to 100 nt. In someembodiments, the crRNA has a length of 12 nt to 25 nt, 13 nt to 25 nt,14 nt to 25 nt, 15 nt to 25 nt, 16 nt to 25 nt, 17 nt to 25 nt, 18 nt to25 nt, 19 nt to 25 nt, 20 nt to 25 nt, 21 nt to 25 nt, or 22 nt to 25nt.

In some embodiments, the crRNA is 17 nt in length, In some embodiments,the crRNA is 18 nt in length. In some embodiments, the crRNA is 19 nt inlength. In some embodiments, the crRNA is 20 nt in length. In someembodiments, the crRNA is 21 nt in length. In some embodiments the crRNAis 22 nt in length. In some embodiments, the crRNA is 23 nt in length.In some embodiments, the crRNA is 24 nt in length. In some embodiments,the crRNA is 25 nt in length.

In some embodiments, the crRNA is at least 17 nt in length, In someembodiments, the crRNA is at least 18 nt in length. In some embodiments,the crRNA is at least 19 nt in length. In some embodiments, the crRNA isat least 20 nt in length. In some embodiments, the crRNA is at least 21nt in length. In some embodiments the crRNA is at least 22 nt in length.In some embodiments, the crRNA is at least 23 nt in length. In someembodiments, the crRNA is at least 24 nt in length. In some embodiments,the crRNA is at least 25 nt in length.

In some embodiments, the guideRNA (gRNA) includes a transacting RNA(tracRNA). Transacting RNA of the subject guideRNA interacts with thecrRNA to recruit a nuclease to the site of a PYR/PYL mutation targetsite. Upon its recruitment to the PYR/PYL mutation target site, thenuclease creates a double strand break (DSB) in the PYR/PYL mutationtarget site. Any suitable tracRNA capable of recruiting a Cas9 to aPYR/PYL mutation target site can be used with the subject gRNA. In someembodiments, the tracRNA is encoded by a nucleotide having a sequencethat is substantially identical to SEQ ID NO: 370. In certainembodiments of the subject method, the tracRNA and the crRNA areintroduced into the plant cells separately (e.g., on differentexpression vectors). In some embodiments, the tracRNA is linked to thecrRNA and introduced into the plant cell as a guideRNA (gRNA).

In another aspect, provided herein is a nucleic acid that includes apolynucleotide encoding any of the subject gRNAs described herein.

In another aspect, provided herein is an expression cassette thatincludes an RNA polymerase promoter operably linked to any of thesubject gRNAs described herein. Any suitable RNA polymerase promotercapable of driving transcription of the nucleic acid encoding thesubject gRNA can be used. In some embodiments, the promoter is aninducible promoter, including, but not limited, to any of the induciblepromoters described herein. In other embodiments, the promoter is aconstitutive promoter, including, but not limited to any of theconstitutive promoters described herein. In yet other embodiments, thepromoter is a tissue-specific promoter, including, but not limited to,any of the tissue-specific promoters described herein. In certainembodiments, the RNA polymerase promoter is an RNA polymerase III(polIII) promoter. In particular embodiments, the polIII promoter is aU3 promoter or a U6 promoter. In certain embodiment, the expressioncassette has the sequence of any one of SEQ ID NOS; 371-373.

Expression Vectors Including gRNA and Cas9 Nuclease

In another aspect, provided herein is an expression vector that includesone or more of the guide RNA (gRNA) expression cassettes provided hereinand an expression cassette including a promoter operably linked to apolynucleotide encoding a CRISPR-associated endonuclease 9 (Cas9). Insome embodiments, the promoter operably linked to the Cas9 is aubiquitin-1 promoter (prUbi-10). In some embodiments, the expressionincludes an expression cassette containing a polynucleotide encoding agRNA having a crRNA that is substantially identical to SEQ ID NOS: 363,364, 365, 366, 367 (see, e.g., FIG. 5). In some embodiments, theexpression vector includes an expression cassette containing apolynucleotide encoding a gRNA having a crRNA that is substantiallyidentical to SEQ ID NOS: 369 (see, e.g., FIG. 6). In some embodiments,the expression vector includes a first expression cassette containing apolynucleotide encoding a gRNA having a crRNA that is substantiallyidentical to SEQ ID NOS: 363, 364, 365, 366, 367; a second expressioncassette containing a polynucleotide encoding a gRNA having a crRNA thatis substantially identical to SEQ ID NO: 369; and a third expressioncassette including a promoter operably linked to a polynucleotideencoding a CRISPR-associated endonuclease 9 (Cas9) (see, e.g., FIG. 7).

Methods of Producing PYR/PYL Variant Plants Using RNA Directed GenomeModification

Expression vectors disclosed herein are useful, for example, forintroducing a mutation in a plant in situ at a genomic PYR/PYL mutationtarget site. Thus, in another aspect, provided herein is a method for ofproducing a plant having a mutation at a genomic PYR/PYL mutation targetsite. In some embodiments, the method includes introducing into plantcells an expression vector encoding for a gRNA and Cas9 as disclosedherein and at least one repair nucleic acid comprising the mutation ofinterest. According to the subject method, the crRNA and tracRNA directsthe nuclease to the PYR/PYL mutation target site in a plant cell genome.Upon its recruitment, the nuclease (e.g., Cas9) creates a double strandbreak at the PYR/PYL mutation target site. The double strand break atthe PYR/PYL mutation target site facilitates homologous recombination ofthe repair nucleic acid containing the mutation of interest with aregion of the plant cell genome that includes the PYR/PYL mutationtarget site, thereby introducing the mutation at the PYR/PYL mutationtarget site. In certain embodiments, the repair nucleic acid has asequence that is substantially identical to any one of the sequence ofSEQ ID NOS:374 to 378. In other embodiments, the repair nucleic acid hasa sequence that is complementary to a sequence that is substantiallyidentical to any one of the sequences of SEQ ID NOS:374 to 386. Inspecific embodiments, the repair nucleic acid has a sequence that issubstantially identical to SEQ ID NO:376. In other embodiments, therepair nucleic acid has a sequence that is complementary to a sequencethat is substantially identical to SEQ ID NO:376. In another embodiment,the repair nucleic acid has a sequence that is substantially identicalto SEQ ID NO:378. In other embodiments, the repair nucleic acid has asequence that is complementary to a sequence that is substantiallyidentical to SEQ ID NO:378. In yet another embodiment of the method, tworepair nucleic acids are introduced, where the repair nucleic acids havesequences that are substantially identical to SEQ ID NO:376 and SEQ IDNO:378. In another embodiment of the method, two repair nucleic acidsare introduced, where the repair nucleic acids have sequences arecomplementary to sequences that are substantially identical to SEQ IDNO:376 and SEQ ID NO:378.

In certain embodiments, the method further includes the step ofselecting plant cells having the mutation. Selection for mutation can beperformed by any useful technique known in the art, including, but notlimited PCR amplification followed by sequencing, capillaryelectrophoresis and Nuclease Serveyer assay. In some embodiments, themethod is for the production of a maize plant.

In yet another aspect, provided herein is a kit for producing a planthaving a mutation in a PYR/PYL nucleic acid as described herein. In someembodiments, the kit includes any one of the subject expression vectorsdisclosed herein and at least one repair nucleic acid, wherein therepair nucleic acid comprises a PYL-E mutation and is capable ofintroducing the PYL-E mutation in situ in a plant cell genome byhomologous recombination upon a Cas9 cleavage event. In certainembodiments, the kit includes a repair nucleic acid that has a sequencethat is substantially identical to SEQ ID NOS:374 to 386.

EXAMPLES

The following examples are offered to illustrate, but not to limit theclaimed invention.

The affinity of a receptor for a target ligand is typically determinedby non-covalent interactions between ligand-binding residues and theligand. Mutations in such residues can have negative, positive orneutral effects on the strength of the receptor-ligand interaction. Theaffinity of a receptor-ligand interaction is intrinsically correlatedwith the concentration of ligand required to elicit biological effects,with high affinity ligands requiring lower concentrations relative tolow affinity ligands. A mutant receptor with increased affinity for aligand can in some cases elicit greater biological effect relative to awild type receptor, when both are activated under identical conditionsby the same concentration of activating ligand. Thus, mutations thatmake a receptor hypersensitive to a ligand can be useful for engineeringorganisms that elicit stronger responses to the ligand relative to wildtype. Furthermore, ABA hypersensitive plants possess enhanced ABAresponses and improved drought tolerance (Wang, Y., et al. Plant J. 43,413-424 (2005)). Based on these considerations, we set out tosystematically establish specific ABA receptor mutations that increaseABA responsiveness. This was done by testing a collection of PYR1variants with all possible single amino acid substitution mutations inligand binding residues. Thus we conducted site-saturated mutagenesis ofABA-contacting residues, which we define as those that are within 5A orABA or ABA-contacting water residues in available X-ray coordinates.This collection of mutants was constructed previously, as described inPCT Application No. PCT/US2012/043121 and Mosquna et al., Proc Natl AcadSci USA 108: 20838-20843 (2011). This collection of mutants was made bymutagenizing a previously described pBD GAL-PYR1 template (Park, S.-Y.,et al. Science 324, 1068-1071 (2011)). In response to ABA, thisparticular plasmid encodes a fusion protein that binds to a co-expressedGAL4 activation domain-HAB1 fusion protein, encoded by the plasmidpACT-HAB1. This binding reconstitutes a functional GAL4 transcriptionalactivator and subsequent transcription of a β-galactosidase reportergene, which in turn enables colorimetric based detection of agonistpromoted receptor-PP2C interaction when lysed cells are exposed to thesubstrate X-gal. The mutant clones were individually transformed into S.cerevisiae strain Y190 containing pACT-HAB1. Yeast transformants wereselected for the presence of plasmids on synthetic dextrose (SD) agarplates lacking Leu and Trp (SD-LT) and examined for PP2C interactions byusing X-gal staining to monitor β-gal reporter gene expression levels.Individual clones were arrayed into 96 well plates and then spotted ontoSD-LT lawn (i.e. one-well) plates containing 0, 0.5 or 5.0 μM (+)-ABA.Each assay plate contained 95 mutant clones and one wild type PYR1positive control clone. The spotted cells were cultured at 30° C. for 48hours after which they were lysed by chloroform and stained with anX-gal solution, as previously described (Park, S.-Y., et al. (2009)Science 324, 1068-1071). Positive were defined as those mutants thatdisplayed staining on 0.5 μM (+)-ABA but no staining on plates lacking(+)-ABA. After this initial screening exercise, all positives cloneswere retested on plates containing 0. 0.25, 0.5 and 1 μM (+)-ABA andstained for galactosidase activity as described above. Mutant clonesshowing detectable staining on 0.5 μM (+)-ABA or lower were scored ashypersensitive mutants. FIG. 1 depicts results of PYR1 mutant-HAB1interactions as assayed in a yeast two-hybrid assay under different ABAconcentrations, with darker spots indicating increased interaction. Thisdata is also summarized below:

Minimal conc. For ABA Mutant SEQ ID NO: Residue WT AA Mutant response(μM) WT 1 1 F61L 124 61 F L 0.25 F61M 125 61 F M 0.25 V81I 126 81 V I0.25 V81Y 127 81 V Y 0.25 I110C 128 110 I C 0.25 I110S 129 110 I S 0.5E141C 130 141 E C 0.5 E141I 131 141 E I 0.25 E141L 132 141 E L 0.25E141M 133 141 E M 0.25 E141N 134 141 E N 0.5 E141T 135 141 E T 0.5 E141V136 141 E V 0.5 E141W 137 141 E W 0.5 E141Y 138 141 E Y 0.25 A160C 139160 A C 0.25 A160I 140 160 A I 0.25 A160V 141 160 A V 0.25

Highly Hypersensitive ABA Receptors Constructed by CombinatorialMutagenesis

Additive or synergistic interactions between the single hypersensitivemutations identified can increase a receptor's sensitivity to ABA. Toidentify potentially beneficial combinations, we used combinatorialmutagenesis to construct receptors that contain combinations of subsetsof the best single mutants identified and then screened these toidentify receptors with increased sensitivity. Mutagenic primerscomplementary to the appropriate regions of PYR1 coding sequence weredesigned to enable the following mutations to be incorporated into aPYR1 template DNA: F61L, F61M, V81I, V81Y, I110C, I110S, E141I, E141L,E141M, E141Y, A160C, A160I, A160V. Equimolar concentrations of theseprimers were combined with a mixture of wild type primers for eachtarget site (4 mol percent relative to the mutant primer pool) and theprimer mix utilized with the QuickChange Lightning Multi Site-DirectedPCR Mutagenesis kit (Agilent, USA) using the pBD-PYR1 template DNA. Theuse of wild type primers in the reaction mixtures enabled, in principle,all double, triple, quadruple and pentuple mutant combinations to besynthesized in the mutagenesis reaction. The reaction products weretransformed into competent E. coli cells to yield a pool of ˜10,000clones, which was then used to prepare plasmid DNA for the mutantlibrary. The pool of mutant plasmids was subsequently introduced intothe previously described pAD-HAB1 MAV99 reporter strain (Peterson, F.C., et al. (2010) Nature Structural & Molecular Biology 17, 1109-1113).In this reporter strain, a GAL4 promoter drives expression of a URA3reporter gene in a genetic background where the endogenous URA3 gene isdisrupted, which enables positive selections using uracil deficientmedia. Thus, mutant clones that encode receptors that can interact withHAB1 can be positively selected using this system. The transformed yeastcells containing the mutant receptor library were next plated ontogrowth medium lacking uracil and containing 50 nM ABA, a concentrationof ABA that is too low to enable growth of control strains. 26 colonieswith uracil-independent growth were identified, which were isolated andre-tested on medium lacking ABA to eliminate cones enablingligand-independent (i.e. constitutive) interactions of receptor withHAB1. Plasmids from yeast cells containing non-constitutive receptorswere isolated and sequenced, which revealed that the following 4 highlyhypersensitive combination mutants had been isolated:

PYR1F61L, A160C, PYR1F61M, A160V, PYR1F61M, I110S, A160V, PYR1F61L,V81I, I110C, A160V.

The plasmids for each of these mutants and their corresponding singlemutations were transformed into the previously described yeast reporterstrain, Y190 pAD-HAB1 (Park, S.-Y., et al. (2009) Science 324,1068-1071). The transformed yeast cells were grown on selective mediacontaining a range of ABA concentrations and cells lysed and stained toreveal β-galactosidase activity, as shown in FIG. 4.

Increased Affinity of a Mutant Hypersensitive Receptor

The ligand sensitivity of PYR1 and HAB1 yeast two hybrid strainsgenerally correlates with receptor affinity. To examine if this was thecase for the hypersensitive mutations identified by our functionalscreens, we conducted isothermal titration calorimetry (ITC) to measurethe heat produced by a mutant receptor-ABA binding reaction and inferthe ligand binding dissociation constant (Kd). The affinity of wild typePYR1 has been previously measured using ITC and estimated to be 97±36 μM(Dupeux et al. 2010). The PYR1-A160V mutant receptor was expressed in E.coli BL21(DE3) as a fusion to the small ubiquitin like protein SUMO,using the vector pSUMO (LifeSensors, USA), which improves the solubilityof proteins in E. coli and contains an NH2-terminal hexa-histidine tagthat facilitates purification using immobilized metal affinitychromatography (IMAC). PYR1 A160V was cloned into pSUMO by using PCRproduct generated from a pBD-PYR1(A160V) yeast two hybrid construct astemplate, and sequence validated. A short flexible linker and tobaccoetch virus (TEV) protease cleavage site (sequenceNH2-GGGSQFGSGGGGGSGSENLYFQS-COOH; SEQ ID NO:411) was incorporated inbetween the SUMO tag and the receptor to enable cleavage of therecombinant protein by TEV protease, which yields PYR1(A160V) plus anNH2-terminal QS appendage. Recombinant SUMO-TEV-PYR1 (A160V) protein wasproduced in E. coli and purified by immobilized metal affinitychromatography as previously described (Okamoto et al., Proceedings ofthe National Academy of Sciences of the United States of America 110,no. 29 (2013): 12132-12137). The purified fusion protein was digestedwith recombinant TEV protease according to established protocols, andthe cleaved protein subsequently separated from both the SUMO tag anduncleaved protein by passing the cleavage reaction over an IMAC column,which does not retain the cleaved PYR1(A160V) product. The cleavedprotein was purified by gel filtration using a Superdex column (GEHealthcare, USA) and concentrated by centrifugal concentration usingAmicon filters (EMD, USA), as previously described (Dupeux et al, TheEMBO Journal 30, no. 20 (2011): 4171-4184). The concentrated protein wasutilized for ITC experiments, using a TA instruments Nano ITC Low Volumeinstrument, repeatedly injecting 2.5 μL of a 600 μM (+)-ABA solutioninto a reaction cell containing 60 μM PYR1(A160V) every 300 seconds for200 minutes. Both the ABA and protein were dissolved in a buffercontaining PBS, 1 mM 2-mercaptoethanol and 0.012% DMSO. The thermogramsgenerated were processed using the instrument's software to a normalizedfit single binding site model, which yielded a Kd of 1.5 μM and abinding stoichiometry of 1.068. These data demonstrate that the A160Vmutation possesses increased ABA affinity relative to wild type PYR1,consistent with the increased sensitivity indicated by yeast two hybridassays.

Targeted Genome Modification

Non-transgenic plants harboring induced mutations in specific genes canbe obtained in multiple ways. Chemical mutagenesis of an organism can beused to create random genome-wide mutations and populations ofmutagenized individuals can be scanned using high-throughput mutationdetection methods to identify individuals harboring specific mutationsin genes of interest. For example, TILLING (Targeting Induced LocalLesions in Genomes) enables an investigator to identify non-naturallyoccurring induced-mutations in a gene by using PCR to amplify a gene ofinterest from 1000s of mutagenized individuals and use hetero-duplexspecific nucleases, such as celery nuclease CEL1, to identify plantsharboring a mutation in the PCR amplified region (McCallum, C. M., etal. (2000). Nat. Biotechnol. 18, 455-457). Many technologies areavailable for polymorphism identification in addition to endonucleases,including direct sequencing of PCR products obtained from mutagenizedindividuals.

To identify maize plants containing ABA receptors with increasedsensitivity an EMS mutagenized population is created and from thispopulation all ABA receptor genes are PCR amplified from 1000s ofmutagenized plants. The amplified products are scanned for polymorphismsusing TILLING methodology and polymorphic fragments identified aresequenced to define the specific mutations present. From this,individuals harboring mutations corresponding to the polymorphismsdescribed in this application are identified.

The most likely mutants to be obtained using this strategy are thosethat can be encoded by a single nucleotide substitution, which can beestablished by examining the codon table. For example, receptors withmutations homologous to F61L or F61M in PYR1 can be obtained in receptorhomologs by screening for different single nucleotide substitutionsdepending on the gene sequence, such as UUU->CUU, or UUC->CUC. The sameis true for A160V (GCN->GUN), V81I (GUU->AUU, GUC->AUC, GUA->AUA), V81Y(GUU->UUU, GUC->UUC). In principle, any single mutation can be isolatedby chemical mutagenesis TILLING, but in practice the subset of changesthat can arise by a single nucleotide substitution are most likely to beobtained. The examples provided above are representative, notexhaustive, and other single nucleotide substitutions enabling desiredmutations, such as E141V and I110S, are also possible.

Other mutation induction systems can be used to target mutations inspecific genes, such as genome editing methods, which have theadvantages of increasing the frequency of single and multiple mutationsat a defined target site (Lozano-Juste, J., and Cutler, S. R. (2014)Trends in Plant Science 19, 284-287). The sequence-specific introductionof a double stranded DNA break (DSB) in a genome leads to therecruitment of DNA repair factors at the breakage site, which thenrepair lesion by either the error-prone non-homologous end joining(NHEJ) or homologous recombination (HR) pathways. NHEJ repairs thebreaks, but is imprecise and often creates diverse mutations at andaround the DSB. In cells in which the HR machinery repairs the DSB,sequences with homology flanking the DSB, including exogenously suppliedsequences, can be incorporated at the region of the DSB. DSBs cantherefore be leveraged by geneticists to increase the frequency ofmutations at defined sites, however intrinsic differences between therelative roles of HR and NHEJ can affect the mutation types at a targetslocus. A number of technologies have been developed to create DSBs atspecific sites including synthetic zinc finger nucleases (ZFNs),transcription activator-like endonucleases (TALENs) and most recentlythe clustered regularly interspaced short palindromic repeats(CRISPR)/CRISPR-associated protein 9 (Cas9) system. This system is basedon a bacterial immune system against invading bacteriophages in which acomplex of 2 small RNAs, the CRISPR-RNA (crRNA) and the transactivatingcrRNA (tracrRNA) directs a nuclease (Cas9) to a specific DNA sequencecomplementary to the crRNA. Using any of these systems, an investigatorcan create DSBs at pre-determined sites in cells expressing the genomeediting constructs. In order for homologous recombination to occur, aDNA cassette homologous to the targeted site must be provided,preferably at a high concentration so that HR is favored or NHEJ.Multiple strategies are conceivable for realizing this, includingtemplate delivery using agrobacterium mediated transformation orparticle bombardment of DNA templates, and one recently described methoduses a modified viral genome to provide the double stranded DNAtemplate. For example, Baltes et al. 2014 (Baltes, N. J., et al. (2014)Plant Cell 26, 151-163) recently demonstrated that an engineeredgeminivirus that was introduced into plant cells using Agrobacteriummediated transformation could be engineered to produce DNA recombinationtemplates in cells where a ZFN was co-expressed.

In some aspects, once DSBs have been created using any number oftechnologies, such sites can be exploited to facilitate isolation oftargeted genetic changes by either homologous recombination ofnucleotide substitutions, deletions or insertions. For example, ABAreceptor genes can be targeted using genome editing technologies andprogeny plants of the mutagenized plants be screened using the methodsoutlined above to identify mutations at sites that increase ABAsensitivity. Delivery of genome editing constructs into organisms caninvolve both unstable transient expression constructs or stableintegration of constructs into genomes delivered by Agrobacteriummediated transformation. In the latter case, stable transgenic plantscan be used to express genome-editing constructs in plants to increasemutation frequencies at the target site. Once the desired mutants areisolated through polymorphism scans (analogous to those used inTILLING), individuals can be back crossed wild type lines to segregateaway transgenic insertion events.

Conceptually, these methods are analogous to TILLING and the methods foridentifying defined mutations would be similar, however because of thetargeted nature of these methods, the frequency of mutations at definedsites will be higher and mutations involving changes of more than asingle base pair can be identified more readily.

Targeted Amino Acid Modification of Maize ABA Receptors Mediated byCRISPR-Cas9 1. Maize ABA Receptor (ZmPYL) Target Gene Modification

In vivo modification of plant ABA receptors is described using maizeZmPYL genes as an example. Maize genome contains more than 10 ABAreceptors (ZmPYL-A to ZmPYL-P) that share several highly conserved aminoacids with AtPYL1. To obtain ABA hypersensitive mutations in theendogenous ZmPYL-E (GRMZM2G165567) gene, two amino acids (V89 and E149)are chosen as targets for sequence-specific mutagenesis into desiredmutant amino acids, alanine and leucine (V89A and E149L), respectively,using homology-directed gene repair mediated by sequence-specificnucleases and donor DNA template. Currently, there are severaltechnology platforms for making sequence-specific nucleases, includingfor example zinc-finger nuclease, TALE nuclease, CRISPR-Cas9 andengineered meganuclease (Puchta and Fauser (2014), Synthetic nucleasesfor genome engineering in plants: prospects for a bright future. PlantJournal 78:727-741; Chen and Gao (2014) Targeted genome modificationtechnologies and their applications in crop improvements. Plant CellRep. 33:575-583), any of which can be used to produce a plant comprisingan in situ hypersensitive mutation in a genomic coding sequence PYR/PYLpolypeptide as described herein.

The following examples describe the use of CRISPR-Cas9 system for makingtargeted gene modification in endogenous ZmPYL-E gene.CRISPR-Cas9-mediated gene modification requires these components: Cas9nuclease, crRNA (CRISPR RNA) recognizing the mutagenesis target, tracRNA(transactivating RNA) and repair donor DNA template molecule. Foreasiness of use, crRNA and tracRNA are fused and delivered as a singleguide RNA molecule (gRNA or sgRNA) [Sander and Joung (2014) CRISPR-Cassystems for editing, regulating and targeting genomes. 32:347-355].

2. Optimization of Cas9 and its Expression in Maize Cells

In order to achieve good expression in maize cells, Type II Cas9 genefrom Streptococcus pyogenes SF370 is optimized with maize-preferredcodons. Nuclear localization signal is also incorporated into theC-terminus of Cas9 to improve its targeting to nucleus. Below is theoptimized Cas9 sequence (cBCas9Nu-01, aka, cCas9-01). To express Cas9 inmaize cells, the maize-optimized Cas9 gene (cBCas9Nu-01) is placed underthe control of maize ubiquitin-1 promoter (prUbi1-10) and is followed bya terminator sequences (tNOS) (FIG. 5).

3. gRNA Design and Expression3.1 gRNAs for Mediating V89A Modification: Structure and its Expression

For targeted V89A modification, crRNAs of at least 17 nucleotides (nt)long are designed against the maize ZmPYL-E genomic target sequence(5′-CGCGA CGTCA ACGTC AAGAC-3′) (SEQ ID NO:362) preceding the 5′-CGG-3′PAM (protospacer adjacent motif) sequence for Cas9-mediated targetrecognition. For example, gRNAs of 17-nt (5′-GA CGUCA ACGUC AAGAC-3′)(SEQ ID NO:363), 18-nt (5′-CGA CGUCA ACGUC AAGAC-3′) (SEQ ID NO:364),19-nt (5′-GCGA CGUCA ACGUC AAGAC-3′) (SEQ ID NO:365), 20-nt (5′-CGCGACGUCA ACGUC AAGAC-3′) (SEQ ID NO:366) or 21-nt (5′-G CGCGA CGUCA ACGUCAAGAC-3′) (SEQ ID NO:367) can be used to guide Cas9 cleavage of theZmPYL-E target. crRNA is co-delivered with tracRNA and Cas9 protein ormRNA to mediate target site cleavage. Preferably, crRNA molecule isfused with tracRNA molecule covalently into a single guide RNA (gRNA).gRNAs can be synthesized chemically or produced by in vitrotranscription. In vitro produced gRNAs can be used directly for physicaldelivery such as biolistic bombardment with Cas9 RNA or protein tomediate target cleavage and homology-directed target modification ifrepair donor oligonucleotide is co-delivered. More preferably, gRNA isproduced in planta from DNA expression cassette comprising RNApolymerase III (PolIII) promoter such as plant U3 and U6 promoters suchas rice U3 and U6 promoters (prOsU3 and prOsU6). For prOsU3, thetranscription start begins with nucleotide A, whereas for prOsU6, thetranscription starts with nucleotide G (Shan et al. (2013) NatureBiotechnology 31: 686-688; Xie and Yang (2013) Molecular Plant6:1975-1983). For example, to produce gRNA targeting the endogenousZmPYKL-E sequence (5′-CGCGA CGTCA ACGTC AAGAC-3′) (SEQ ID NO:362), 19-ntDNA oligonucleotides (5′-GCGA CGTCA ACGTC AAGAC-3′) (SEQ ID NO:365) or21-nt oligonucleotides (5′-G CGCGA CGTCA ACGTC AAGAC-3′) (SEQ ID NO:367)is fused to the DNA sequences encoding tracRNA scaffold ((5′-GTTTT AGAGCTAGAA ATAGC AAGTT AAAAT AAGGC TAGTC CGTTA TCAAC TTGAA AAAGT GGCAC CGAGTCGGTG C-3′) (SEQ ID NO: 370) and PolIII termination sequences (5′-GTTTTAGAGC TAGAA ATAGC AAGTT AAAAT AAGGC TAGTC CGTTA TCAAC TTGAA AAAGT GGCACCGAGT CGGTG CTTTT TTTTT-3′(SEQ ID NO:413), Mali et al. (2013) Science339:823-826) and placed under the control of rice polymerase IIIpromoter U3 (prOsU3) or U6 (prOsU6). Below is the sequence (SEQ IDNO:371) of the expression cassette comprising of prOsU3 and codingsequences for the gRNA comprising the 19-nt V89A crRNA (underlined)fused with tracRNA. This sequence is cloned into biolistictransformation vector along with the Cas9 expression cassette to formvector pZmPYLE-V89A (FIG. 5).

(SEQ ID NO: 371) 5′-GGGAT CTTTA AACAT ACGAA CAGAT CACTT AAAGTTCTTC TGAAG CAACT TAAAG TTATC AGGCA TGCAT GGATCTTGGA GGAAT CAGAT GTGCA GTCAG GGACC ATAGC ACAGGACAGG CGTCT TCTAC TGGTG CTACC AGCAA ATGCT GGAAGCCGGG AACAC TGGGT ACGTT GGAAA CCACG TGATG TGGAGTAAGA TAAAC TGTAG GAGAA AAGCA TTTCG TAGTG GGCCATGAAG CCTTT CAGGA CATGT ATTGC AGTAT GGGCC GGCCCATTAC GCAAT TGGAC GACAA CAAAG ACTAG TATTA GTACCACCTC GGCTA TCCAC ATAGA TCAAA GCTGG TTTAA AAGAGTTGTG CAGAT GATCC GTGGC A GCGA CGTCA ACGTC AAGACGTTTT AGAGC TAGAA ATAGC AAGTT AAAAT AAGGC TAGTCCGTTA TCAAC TTGAA AAAGT GGCAC CGAGT CGGTG CTTTT TTTTT-3′

The sequence example below (SEQ ID NO:372) describes the expressioncassette comprising of prOsU6 promoter and coding sequences for a gRNAcomprising the 21-nt V89A crRNA (underlined) and tracRNA.

(SEQ ID NO: 372) 5′-TTTGT GAAAG TTGAA TTACG GCATA GCCGA AGGAATAACA GAATC GTTTC ACACT TTCGT AACAA AGGTC TTCTTATCAT GTTTC AGACG ATGGA GGCAA GGCTG ATCAA AGTGATCAAG CACAT AAACG CATTT TTTTA CCATG TTTCA CTCCATAAGC GTCTG AGATT ATCAC AAGTC ACGTC TAGTA GTTTGATGGT ACACT AGTGA CAATC AGTTC GTGCA GACAG AGCTCATACT TGACT ACTTG AGCGA TTACA GGCGA AAGTG TGAAACGCAT GTGAT GTGGG CTGGG AGGAG GAGAA TATAT ACTAATGGGC CGTAT CCTGA TTTGG GCTGC GTCGG AAGGT GCAGCCCACG CGCGC CGTAC CGCGC GGGTG GCGCT GCTAC CCACTTTAGT CCGTT GGATG GGGAT CCGAT GGTTT GCGCG GTGGCGTTGC GGGGG ATGTT TAGTA CCACA TCGGA AACCG AAAGACGATG GAACC AGCTT ATAAA CCCGC GCGCT GTAGT CAGCT TGCGC GACGT CAACG TCAAG ACGTT TTAGA GCTAG AAATAGCAAG TTAAA ATAAG GCTAG TCCGT TATCA ACTTG AAAAAGTGGC ACCGA GTCGG TGCTTTT TTTTT-3′3.2 gRNA for Mediating E149L Modification: Structure and its Expression

For targeted E149L modification of the maize ZmPYL-E, the two underlinedbases in the maize genomic target sequence (5′-GCACC CTGGT GATCG AGTCGTTCGT GGTCG-3′) (SEQ ID NO:368) needs to be converted into CT to formmutant sequence (5′-GCACC CTGGT GATCC TGTCG TTCGT GGTCG-3′ (SEQ IDNO:412)). In order to achieve that, an expression cassette for asequence coding for the 20-nt guide RNA (5′-CCTGG TGATC CTGTC GTTCG-3′,xZmPYLE-E149L) (SEQ ID NO:369), tracRNA scaffold and PolIII terminationsequences (5′-GTTTT AGAGC TAGAA ATAGC AAGTT AAAAT AAGGC TAGTC CGTTATCAAC TTGAA AAAGT GGCAC CGAGT CGGTG CTTTT TTTTT-3′ (SEQ ID NO:413), Maliet al. (2013) Science 339:823-826) was placed under the control of ricepolymerase III promoter U6 (prOsU6) as shown in FIG. 6. prOsU6 promoterinitiates transcription after nucleotide G. In FIG. 6, the prOsU6-E149LgRNA expression cassette has the following sequences (SEQ ID NO:373)with the 20 bp targeting guide sequence (xZmPYLE-E149L or xZmPYLe, SEQID NO: 369) underlined.

(SEQ ID NO: 373) 5′-TTTGT GAAAG TTGAA TTACG GCATA GCCGA AGGAATAACA GAATC GTTTC ACACT TTCGT AACAA AGGTC TTCTTATCAT GTTTC AGACG ATGGA GGCAA GGCTG ATCAA AGTGATCAAG CACAT AAACG CATTT TTTTA CCATG TTTCA CTCCATAAGC GTCTG AGATT ATCAC AAGTC ACGTC TAGTA GTTTGATGGT ACACT AGTGA CAATC AGTTC GTGCA GACAG AGCTCATACT TGACT ACTTG AGCGA TTACA GGCGA AAGTG TGAAACGCAT GTGAT GTGGG CTGGG AGGAG GAGAA TATAT ACTAATGGGC CGTAT CCTGA TTTGG GCTGC GTCGG AAGGT GCAGCCCACG CGCGC CGTAC CGCGC GGGTG GCGCT GCTAC CCACTTTAGT CCGTT GGATG GGGAT CCGAT GGTTT GCGCG GTGGCGTTGC GGGGG ATGTT TAGTA CCACA TCGGA AACCG AAAGACGATG GAACC AGCTT ATAAA CCCGC GCGCT GTAGT CAGCT TGCCT GGTGA TCGAG TCGTT CGGTT TTAGA GCTAG AAATAGCAAG TTAAA ATAAG GCTAG TCCGT TATCA ACTTG AAAAAGTGGC ACCGA GTCGG TGCTT TTTTT TT-3′

Alternatively, the guide RNA can also be expressed from a differentpolymerase III promoter like rice U3 promoter (prOsU3) which initiatestranscription after nucleotide A. The prOsU3-E149L gRNA expressioncassette has the following sequences (SEQ ID NO:374) with the 20 bptargeting guide sequence (xZmPYLE-E149L or xZmPYLe, SEQ ID NO: 369)underlined. This prOsU3-E149L gRNA expression cassette along with PMIselectable marker gene cassette and prSoUbi4 driven Cas9 gene expressioncassette are inserted into binary vector backbone to form transformationvector 23190 (FIG. 8).

(SEQ ID NO: 374) 5′-GGGAT CTTTA AACAT ACGAA CAGAT CACTT AAAGTTCTTC TGAAG CAACT TAAAG TTATC AGGCA TGCAT GGATCTTGGA GGAAT CAGAT GTGCA GTCAG GGACC ATAGC ACAGGACAGG CGTCT TCTAC TGGTG CTACC AGCAA ATGCT GGAAGCCGGG AACAC TGGGT ACGTT GGAAA CCACG TGATG TGGAGTAAGA TAAAC TGTAG GAGAA AAGCA TTTCG TAGTG GGCCATGAAG CCTTT CAGGA CATGT ATTGC AGTAT GGGCC GGCCCATTAC GCAAT TGGAC GACAA CAAAG ACTAG TATTA GTACCACCTC GGCTA TCCAC ATAGA TCAAA GCTGG TTTAA AAGAGTTGTG CAGAT GATCC GTGGC A CCTG GTGAT CGAGT CGTTCGGTTT TAGAG CTAGA AATAG CAAGT TAAAA TAAGG CTAGTCCGTT ATCAA CTTGA AAAAG TGGCA CCGAG TCGGT GCTTT TTTTT T-3′4. Generation of Mutants with Targeted Genomic Sequence Modification inZmPYL-E Gene4.1 Generation of Targeted Mutation V89A in ZmPYL-E Gene with BiolisticBombardment

For target gene sequence modification mediated by homology-directedrepair, donor DNA molecule needs to be co-delivered with Cas9 and gRNA.DNA molecule with at least 15 nucleotides flanking the Cas9 cleavagesite and containing the intended mutant nucleotide(s) is used as repairdonor. For modification of the target sequence 5′-CGCGA CGTCA ACGTCAA/GAC-3′ to result in V89A mutation, the single underlined residue Tneeds to be converted to C so valine at position 89 (V89, GTC) ischanged to alanine (A89, GCC). Since the intended Cas9 cleavage site(indicated by /) is 9 nucleotides downstream, preferably, the repair DNAmolecule should contain sequences at least 15-nt upstream of TCA and15-nt downstream of the underlined A in AA/GAC as in this sequence(5′-GCAGCCT GCGCGACGCC AACGTCAA/GA CCGGCCTGCC GGC-3′) (SEQ ID NO:375).More preferably, the repair DNA molecule should contain sequences withat least 20-nt upstream of TCA and at least 20-nt downstream of theunderlined A in AA/GAC as outlined in this sequence (5′-GG TCGGCAGCCTGCGCGACGCC AACGTCAA/GA CCGGCCTGCC GGCGACGA-3′) (SEQ ID NO:376). Morepreferably, the repair DNA molecule should contain sequences with morethan 30-nt upstream of TCA and more than 30-nt downstream of theunderlined A in AA/GAC as outlined in this sequence (5′-AC CAGCTC GAGGTCGGCAGCCT GCGCGACGCC AACGTCAA/GA CCGGCCTGCC GGCGACGACC AGAACCGA-3′)(SEQ ID NO:377). Most preferably, the repair DNA molecule should containsequences with more than 50-nt upstream of TCA and more than 50-ntdownstream of the underlined A in AA/GAC as indicated in this sequence(5′-GA ACTGCGTCGT GCGCGGGGAC CAGCTC GAGG TCGGCAGCCT GCGCGACGCCAACGTCAA/GA CCGGCCTGCC GGCGACGACC AGAACCGAGC GCCTCGAGCA GCTCGACGA-3′)(SEQ ID NO:378). It should be noted that oligonucletoides with sequencescorresponding to the opposite strand of SEQ ID NO:375 to SEQ ID NO:378can also be used for mediating targeted V89A mutation.

To generate plants carrying V89A mutation, the above described repairdonor DNA oligonucleotide (5′-AC CAGCTC GAGG TCGGCAGCCT GCGCGACGCCAACGTCAA/GA CCGGCCTGCC GGCGACGACC AGAACCGA-3′) (SEQ ID NO:377) thatcomprise sequences 30-nt upstream of TCA and 30-nt downstream of theunderlined A in AA/GAC is co-precipitated with pZmPYLE-V89A vector(FIG. 1) onto gold particles and bombarded into immature maize embryos(genotype A188, HiII or other applicable varieties). Methods for maizeimmature embryo bombardment, callus induction tissue regeneration androoting methods have been described previously except here no mannoseselection is required (Wright et al., 2001, Efficient biolistictransformation of maize (Zea mays L.) and wheat (Triticum aestivum L.)using the phosphomannose isomerase gene, pmi, as the selectable marker.Plant Cell Reports 20:429-436.). Briefly, immature embryos are isolatedfrom harvested immature ears at about 9-12 days after pollination andpre-cultured for 3 to 5 days on osmoticum media. Pre-cultured embryosare then bombarded with DNA vector ZmPYLE-V89A and the donoroligonucleotide using BioRad PDS-1000 Biolistic particle deliverysystem. Bombarded embryos are then incubated in callus induction mediaand then moved onto regeneration media to induce shoot formation. Shootsare then moved to rooting media. Preferably but not essential, aselectable marker gene cassette like PMI is also added to theZmPYLE-V89A vector so only transformed cells containing an integratedgRNA or Cas9 expression cassette will be selected for regeneration.Samples are then harvested from regenerated plants for genotyping toidentify plants containing the desired V89A mutation in the ZmPYL-Egene. Genotyping can be done with one or more of the standard mutationdetection methods such as PCR amplification followed by sequencing,capillary electrophoresis and Nuclease Surveyer assay.

ZmPYLE-V89A vector carries the gRNA and Cas9 expression cassettes canalso be delivered into maize cells using other physical delivery methodsuch as protoplast transformation and silicon carbide whisker-mediatedtransformation. The repair donor DNA molecule can also be delivered intocells in the form of single- or double-stranded molecule that is presentas part of a recombinant DNA molecule such as restriction fragment orplasmid or T-DNA or viral replicon for generation of transformed cellsusing methodologies known in the art. Alternatively, gRNA and Cas9expression vectors and repair donor vector can be transformed into maizecells with Agrobacterium-mediated transformation. It should be notedthat for targeted modification, no integration of Cas9 or gRNAexpression vector is required or even preferred. Therefore, thesevectors can be delivered transiently by biolistic transformation orAgrobacterium-mediated transformation.

4.2 Generation of Targeted Mutation E149L in ZmPYL-E Gene with Biolisticand Agrobacterium-Mediated Transformation

Similar to the above example (Section 4.1) for generating ZmPYLE-V89Amutation, targeted E149L mutation (Table 1) can be introduced intoZmPYL-E gene using biolistic bombardment using DNA vectors carrying Cas9and gRNA expression cassettes such as these shown in FIG. 6 and FIG. 8along with repair donor DNA sequences containing the desired mutationsuch as in the form of purified oligonucleotide with this sequence(ZmPYL-Eb, SEQ ID NO:379, 5′-TGACG GGAGG CCGGG CACCC TGGTG ATCCT GTCGTTCGTA GTCGA TGTGC CTGAT GGCAA-3′, Table 2). Other forms of repair donoroligonucleotides can be used too. For example, the oligonucleotides canbe longer or in the complimentary strand or contain chemicalmodifications (e.g. phosphorothioate or methylphosphonate) to enhancestability or affinity to the target sequences. Chemically modifiedoligonucletoides have been described (Deleavey and Damha, 2012,Chemistry & Biology, http://dx.doi.org/10.1016/j.chembiol.2012.07.011).To demonstrate utility of such chemically modified oligonucleotides,experiments were done using oligonucleotides with sequences from thenon-coding strand and also containing phosphorothioate linkage (Table 2,ZmPYL-Ec-NT-PM, SEQ ID NO:380, 5′-T*T*C*GT GTTGC CATCA GGCAC ATCGA CTACGAACGA CAGGA TCACC AGGGT GCCCG GCCTC CCGTC AATG*C* T*C-3′, * denotes thepresence of phosphorothioate linkage between nucleotides).

Targeted mutation E149L in ZmPYL-E gene can also be generated with DNAmolecules delivered via Agrobacterium. Agrobacterium-mediatedtransformation methods have been described elsewhere (Ishida et al.(1996). High efficiency transformation of maize (Zea mays L.) mediatedby Agrobacterium tumefaciens. Nat. Biotechnol. 14, 745-750; Negrotto etal. (2000). Theuse of phosphomannose-isomerase as a selectable marker torecover transgenic maize plants (Zea mays L.) via Agrobacteriumtransformation. Plant Cell Rep. 19, 798-803.). Briefly, the prOsU6-E149L(SEQ ID NO:373) or prOsU3-E148L (SEQ ID NO:374) gRNA expression cassetteis cloned into a binary vector carrying PMI selectable marker cassetteand also an expression cassette for Cas9 with maize preferred codonsforming transformation vector pZmPYLE-E149L and 23190 (FIG. 6, FIG. 8,Table 1). These vectors can be used to deliver Cas9 and gRNA expressioncassettes into maize cells with Agrobacterium-mediated transformation.The repair donor DNA molecule containing the intended mutant sequences(5′-TGACG GGAGG CCGGG CACCC TGGTG ATCCT GTCGT TCGTA GTCGA TGTGC CTGATGGCAA-3′) (SEQ ID NO:379) is co-delivered into cells from a separateT-DNA molecule. However, it can be also be inserted into the T-DNAregion next to the gRNA and Cas9 expression cassettes in the binaryvector pZmPYLE-E149L or 23190 (FIG. 2). The donor repair template canalso be delivered in the form of viral replicon derived from anotherT-DNA (Baltes et al. 2014, DNA replicons for plant genome engineering.Plant Cell. 26:151-163). PMI marker is used to select for transgenicplants with integrated Cas9 or gRNA expression cassette. However, itshould be noted that stable transformation of transformation vectors isnot essential or even preferred for generating desired mutations as longas enough plants are screened since transient expression of Cas9 andgRNA is sufficient to result in cleavage of the chromosomal targetsequence to induce DNA repair. However, it should be noted that fortargeted modification, no integration of Cas9 or gRNA expression vectoris required or even preferred.

4.3 Generation of Multiple Amino Acid Modifications in ZmPYL-E GeneSimultaneously

It should be noted that more than one target can be modified at the sametime if gRNAs and repair donors for multiple target sequences arepresent at the same time. For example, both V89A and E149L mutations canbe obtained by co-bombarding vector pZmPYLE-V89A-E149L containingexpression cassettes for Cas9 and two gRNAs (FIG. 7) along with bothrepair donor DNA templates, V89A oligonucleotide (5′-AC CAGCTC GAGGTCGGCAGCCT GCGCGACGCC AACGTCAA/GA CCGGCCTGCC GGCGACGACC AGAACCGA-3′)(SEQID NO:377) and E149L oligonucleotides ODN-ZmPYL-Eb (5′-TGACG GGAGG CCGGGCACCC TGGTG ATCCT GTCGT TCGTA GTCGA TGTGC CTGAT GGCAA-3′) (SEQ IDNO:379) or ODN-ZmPYL-Ec-NT-PM (SEQ ID NO:380, 5′-T*T*C*GT GTTGC CATCAGGCAC ATCGA CTACG AACGA CAGGA TCACC AGGGT GCCCG GCCTC CCGTC AATG*C*T*C-3′, * denotes the presence of phosphorothioate linkage betweennucleotides).

As described for generating plants with single mutations, bombardedembryos are then incubated in callus induction media and then moved ontoregeneration media to induce shoot formation. Shoots are then moved torooting media. PMI marker can be used to select for transgenic plantswith integrated Cas9 or gRNA expression cassette. However, it should benoted again that stable transformation of transformation vectors is notessential or even preferred for generating desired mutations as long asenough plants are screened to identify plants with desired mutationssince transient expression of Cas9 and gRNA is sufficient to result incleavage of the chromosomal target sequence to induce DNA repair.Samples are then harvested from regenerated plants for genotyping toidentify plants containing the desired V89A and E149L mutations in theZmPYL-E gene. Genotyping can be done with one or more of the standardmutation detection methods such as PCR amplification followed bysequencing, capillary electrophoresis and Nuclease Surveyer assay.

4.4 Generation of Additional Targeted Mutations at V89 Position inZmPYL-E Gene

Alternate site-directed changes can be introduced at the V89 position ofthe ZmPYL-E to obtain ABA hypersensitive mutations by using similarmethod described above for creating V89A mutation except that repairdonor oligonucleotide sequences need to be changed to introduce thecorresponding mutations. For example, V89I and V89Y mutations can beintroduced by using the same gRNAs (SEQ ID NOS: 363 to 367) to guideCas9 cleavage of the ZmPYL-E target. Expressing cassettes for gRNA andCas9 can be delivered into maize cells simultaneously by any physical orbiological methods such as biolistic bombardment orAgrobacterium-mediated transformation. For introduction of V89Imutation, the single underlined residue Gin the ZmPYL-E genomic targetsequence 5′-CGCGA CGTCA ACGTC AA/GAC-3′ needs to be converted to A, sovaline at position 89 (V89, GTC) is changed to isoleucine (I89, ATC).Since the intended Cas9 cleavage site (indicated by /) is 9 nucleotidesdownstream, preferably, the repair DNA molecule should contain sequencesat least 15-nt upstream of GTC and 15-nt downstream of the underlined Ain AA/GAC as in this sequence (5′-GGCAGCCT GCGCGACATC AACGTCAAGACCGGCCTGCC GGC-3′) (SEQ ID NO:381). More preferably, the repair DNAmolecule should contain sequences with at least 20-nt upstream of ATCand at least 20-nt downstream of the underlined A in AAGAC as outlinedin this sequence (5′-AGG TCGGCAGCCT GCGCGACATC AACGTCAAGA CCGGCCTGCCGGCGACGA-3′) (SEQ ID NO:382). More preferably, the repair DNA moleculeshould contain sequences with more than 30-nt upstream of ATC and morethan 30-nt downstream of the underlined A in AAGAC as outlined in thissequence (5′-GAC CAGCTC GAGG TCGGCAGCCT GCGCGACATC AACGTCAAGA CCGGCCTGCCGGCGACGACC AGAACCGA-3′) (SEQ ID NO:383). Most preferably, the repair DNAmolecule should contain sequences with more than 50-nt upstream of ATCand more than 50-nt downstream of the underlined A in AAGAC as indicatedin this sequence (5′-GGA ACTGCGTCGT GCGCGGGGAC CAGCTC GAGG TCGGCAGCCTGCGCGACATC AACGTCAAGA CCGGCCTGCC GGCGACGACC AGAACCGAGC GCCTCGAGCAGCTCGACGA-3′) (SEQ ID NO:384).

For introduction of V89Y mutation, the two underlined residues GT in themaize genomic target sequence 5′-CGCGA CGTCA ACGTC AA/GAC-3′ need to beconverted to TA, so the valine residue at position 89 (V89, GTC) ischanged to tyrosine (Y89, TAC). Since the intended Cas9 cleavage site(indicated by /) is 9 nucleotides downstream, preferably, the repair DNAmolecule should contain sequences at least 15-nt upstream of GTC and15-nt downstream of the underlined A in AA/GAC as in this sequence(5′-GGCAGCCT GCGCGACTAC AACGTCAAGA CCGGCCTGCC GGC-3′) (SEQ ID NO:385).More preferably, the repair DNA molecule should contain sequences withat least 20-nt upstream of TAC and at least 20-nt downstream of theunderlined A in AAGAC as outlined in this sequence (5′-AGG TCGGCAGCCTGCGCGACTAC AACGTCAAGA CCGGCCTGCC GGCGACGA-3′) (SEQ ID NO:386). Morepreferably, the repair DNA molecule should contain sequences with morethan 30-nt upstream of TAC and more than 30-nt downstream of theunderlined A in AAGAC as outlined in this sequence (5′-GAC CAGCTC GAGGTCGGCAGCCT GCGCGACTAC AACGTCAAGA CCGGCCTGCC GGCGACGACC AGAACCGA-3′) (SEQID NO:387). Most preferably, the repair DNA molecule should containsequences with more than 50-nt upstream of TAC and more than 50-ntdownstream of the underlined A in AA/GAC as indicated in this sequence(5′-GGA ACTGCGTCGT GCGCGGGGAC CAGCTC GAGG TCGGCAGCCT GCGCGACTACAACGTCAAGA CCGGCCTGCC GGCGACGACC AGAACCGAGC GCCTCGAGCA GCTCGACGA-3′)(SEQ ID NO:388).

Similarly, double mutants containing V89I (or V89Y) and E149L (see,e.g., SEQ ID NOS:390, 391 and 392) can be obtained by transforming maizecells with vectors containing expression cassettes for Cas9 and twogRNAs along with oligonucleotides to introduce corresponding mutations(E149L, V89I or V89Y) as described above in section 4.3.

5. Generation of Targeted E169L Genomic Sequence Modification inAdditional ZmPYL Gene Family Members, ZmPYL-D, ZmPYL-F and ZmPYL-J

5.1 Mutagenesis Targets and gRNA Design

Similar to examples described above for endogenous ZmPYL-E gene (Example4 and Table 1), additional ZmPYL gene family members were also chosenfor targeted genome editing to replace specific nucleotides so the aminoacid residue corresponding to E¹⁶⁹ in the ABA receptors (ZmPYL-D,ZmPYL-F and ZmPYL-J) is changed to a hypersenstive form L¹⁶⁹. Theseintended changes are summarized in Table 1. These experiments aimed tomodify the corresponding conserved amino acid residue E (glutamic acid)into L (Leucine) in homologous ZmPYL genes.

TABLE 1 ZmPYL mutations and gRNA sequences and transformation vectorsDesired Trans- WT maize mutant gRNA target sequence formation ZmPYLprotein protein in transformation vector vector gene sequence sequence(SEQ. ID. NO. and notes) name ZmPYL-E LVIE ¹⁴⁹SFV LVIL ¹⁴⁹SFV5′-cctgg tgatc gagtc gttcg-3′ 23190 (GRMZM2G16(SEQ. ID. NO: 369; target site 5567_P02) in coding strand, basereplacement 5 bp away from the Cas9 cleavage site) ZmPYL-D TLVIE ¹⁶⁹SFVTLVIL ¹⁶⁹SFV 5′-gtcgg ggacg tcgac gacga-3′ 23136 (GRMZM2G04(SEQ. ID. NO: 393; target site 8733_P02) in template strand, basereplacement 8 bp away from the Cas9 cleavage site) ZmPYL-D LVIE ¹⁶⁹SFVLVIL ¹⁶⁹SFV 5′-gaggt catcg acggc cggcc-3′ 23189 (GRMZM2G04(SEQ. ID. NO: 394; target site 8733_P02) in coding strand, basereplacement 19 bp away from the Cas9 cleavage site) ZmPYL-F LVIE ¹⁶⁴SFVLVIL ¹⁶⁴SFV 5′-gctcg tgatc gagtc cttcg  22981 (GRMZM2G05 tgg-3′(SEQ. ID. NO: 395; 3882_P01) longer targeting guide sequence(23 bp), target site in coding strand, base replacement 8 bpaway from the Cas9 cleavage site) ZmPYL-F LVIE ¹⁶⁴SFV LVIL ¹⁶⁴SFV5′-gctcg tgatc gagtc cttcg-3′ 23191 (GRMZM2G05(SEQ. ID. NO: 396; shorter 3882_P01) targeting guide sequence (20 bp),target site in coding strand, base replacement 5 bp away fromthe Cas9 cleavage site) ZmPYL-J VVLE ¹⁴⁸SYV VVLE ¹⁴⁸SYV5′-cgtcg acgac gtagg actcg-3′ 23192 (GRMZM2G15(SEQ. ID. NO: 397; target site 4987_P01) in template strand, basereplacement at the Cas9 cleavage site)5.2 Constructions of Vectors for Expression of gRNAs Targeting ZmPYL-D,ZmPYL-F and ZmPYL-J Genes

Similar to examples described above for constructing 23190 forexpressing gRNA for endogenous ZmPYL-E gene (Example 4), transformationvectors expressing Cas9 and different gRNAs (Table 1) for ZmPYL-D (23136and 23189), ZmPYL-F (22981 and 23191) and ZmPYL-J (23192) genes wereconstructed (FIGS. 9A-9B, 10A-10B and 11). The gRNA targeting sequencefor different ZmPYL genes are listed in Table 1 (SEQ ID NO:393 to 397).In these vectors, the whole gRNA coding regions [˜20 nucleotidetargeting guides (SEQ ID NO:393 to 397), tracRNA scaffold and PolIIItermination sequences (5′-GTTTT AGAGC TAGAA ATAGC AAGTT AAAAT AAGGCTAGTC CGTTA TCAAC TTGAA AAAGT GGCAC CGAGT CGGTG CTTTT TTTTT-3′)] wereplaced under the control of rice polymerase III U3 promoter (prOsU3).These vectors also contain a PMI selectable marker gene cassette forselecting stable transformants. These vectors can be used fortransformation mediated by Agrobacterium-mediated transformation or useddirectly for particle bomdbarment.

5.3 Generation of Genome Edited Novel Alleles (Targeted Mutagenesis andAllele Replacement Mutants) Mediated CRISPR-Cas in ZmPYL-D, ZmPYL-F andZmPYL-J Genes

Novel alleles including targeted mutagenesis and allele replacementmutants can be generated via CRISPR-Cas system in the presence of repairdonor DNA by Agrobacterium-mediated transformation or particlebomdbarment as described in Example 4 for ZmPYL-E. Here specificexamples are provided for targeted notations in ZmPYL-D, ZmPYL-F andZmPYL-J genes using biolistic co-delivery of transformation vectors(Table 1 and FIG. 9A-B to 11) and repair donor oligodeoxynucleotideswith desired mutations (Table 2 and Seq ID NO:398 to 410).Oligodeoxynucleotides (ODNs) of different length, strand (coding andnon-coding template) or modification (with and without phosphorothioatelinkage modification at the ends) (Seq ID NO:397 to 409) were used tomediate mutagenesis in different ZmPYL genes.

TABLE 2 Repair donor DNA oligonucleotide sequences Cas9 and gRNA Oligo-expression deoxynucleotide Length ZmPYL gene vector(s) (ODN) (nt) NotesSeq. ID. No. ZmPYL-D 23136 ODN-ZmPYL-Dc 75 PAM #1 and target site intemplate strand, Seq. ID. No. 398 base replacement 8 bp away from theCas9 cleavage site ZmPYL-D 23136 ODN-ZmPYL-Dd- 75 PAM#1 and target sitein template strand, base Seq. ID. No. 399 NT replacement 8 bp away fromthe Cas9 cleavage site; PAM in donor ODN removed ZmPYL-D 23136ODN-ZmPYL-Dd- 75 PAM#1 and target site in coding strand, base Seq. ID.No. 400 NT-PM replacement 8 bp away from the Cas9 cleavage site; PAM indonor ODN removed; ODN with phosphorothioate linkage modificationZmPYL-D 23189 ODN-ZmPYL-Db 88 PAM #2 and target site in coding strand,base Seq. ID. No. 401 replacement 19 bp away from the Cas9 cleavagesite; PAM in donor ODN removed; ZmPYL-E 23190 ODN- ZmPYL-Eb 60 Targetsite in coding strand, base replacement Seq. ID. No. 379 5 bp away fromthe Cas9 cleavage site; ODN in non-coding strand; PAM in donor ODNremoved ZmPYL-E 23190 ODN-ZmPYL-Ec- 72 Target site in coding strand,base replacement Seq. ID. No. 380 NT-PM 5 bp away from the Cas9 cleavagesite; ODN with phosphorothioate linkage modification; PAM in donor ODNremoved ZmPYL-F 22981, 23191 ODN-ZmPYL-Fa 60 Target site in codingstrand, base replacement Seq. ID. No. 402 5 or 8 bp away from the Cas9cleavage site; PAM in donor ODN not removed ZmPYL-F 22981, 23191ODN-ZmPYL-Fb 60 Target site in coding strand, base replacement Seq. ID.No. 403 5 or 8 bp away from the Cas9 cleavage site; PAM in donor ODNremoved ZmPYL-F 22981, 23191 ODN-ZmPYL-Fc 77 Target site in codingstrand, base replacement Seq. ID. No. 404 5 or 8 bp away from the Cas9cleavage site; PAM in donor ODN removed ZmPYL-F 22981, 23191ODN-ZmPYL-Fd- 77 Target site in coding strand, base replacement Seq. ID.No. 405 NT 5 or 8 bp away from the Cas9 cleavage site; PAM in donor ODNremoved ZmPYL-F 22981, 23191 ODN-ZmPYL-Fd- 77 Target site in codingstrand, base replacement Seq. ID. No. 406 NT-PM 5 or 8 bp away from theCas9 cleavage site; PAM in donor ODN removed; ODN with phosphorothioatelinkage modification ZmPYL-J 23192 ODN-ZmPYL-Jc 68 Target site intemplate strand, base Seq. ID. No. 407 short replacement at the Cas9cleavage site; ODN in coding strand sequence ZmPYL-J 23192ODN--ZmPYL-Jc- 68 Target site in template strand, base Seq. ID. No. 408NT replacement at the Cas9 cleavage site; ODN in non-coding strandsequence ZmPYL-J 23192 ODN--ZmPYL-Jc- 68 Target site in template strand,base Seq. ID. No. 409 NT-PM replacement at the Cas9 cleavage site; ODNin non-coding strand sequence and with phosphorothioate linkagemodification ZmPYL-J 23192 ODN--ZmPYL-Jc- 88 Target site in templatestrand, base Seq. ID. No. 410 long replacement at the Cas9 cleavagesite; ODN in coding strand sequence

More specifically, the above described transformation vector (Table 2)expressing Cas9 and gRNA is mixed with its corresponding repair donorDNA oligonucleotides (SEQ ID NO:398 to 410) and then precipitated ontogold particles. The coated gold particles are then used to bombardimmature maize embryos of elite inbred transformation variety NP2222(DeFramond A J, et al (2013) Corn Event 5307. U.S. Pat. No. 8,466,346).Other maize genotype such as A188 and HiII can be used as bombardmenttarget tissue source. Methods for maize immature embryo bombardment,callus induction tissue regeneration and rooting methods have beendescribed previously except here no mannose selection is required(Wright et al., 2001, Efficient biolistic transformation of maize (Zeamays L.) and wheat (Triticum aestivum L.) using the phosphomannoseisomerase gene, pmi, as the selectable marker. Plant Cell Reports20:429-436). For example, for mutagenesis of ZmPYL-F gene mediated byCRISP-Cas9, immature embryos are isolated from harvested immature earsat about 9-12 days after pollination and pre-cultured for 3 to 5 days onosmoticum media. Pre-cultured embryos are then bombarded with DNA vector22981 along with one of the oligonucleotides [ODN-ZmPYL-Fa,ODN-ZmPYL-Fb, ODN-ZmPYL-Fc, ODN-ZmPYL-Fd-NT or ODN-ZmPYL-Fd-NT-PM (Seq.ID. NO:402 to 406)] using BioRad PDS-1000 Biolistic particle deliverysystem. Bombarded embryos are then incubated in callus induction mediaand then moved onto mannose selection media. Selected calli are movedonto regeneration media to induce shoot formation. Shoots are then movedto rooting media. Samples are then harvested from regenerated plants forgenotyping to identify plants containing the desired genomic sequencemutation that results in E164L amino acid change in the ZmPYL-F gene.Table 3 lists different experiments for targeted mutagenesis and allelereplacement of different ZmPYL genes. In some experiments, gRNA and Cas9expression vector was co-transformed with ZsGreen fluorescent proteinvector 12672 for assessing gene delivery efficiency. In some otherexperiments, two or more gRNA expression vectors were co-delivered withtwo or more repair donor oligodexynucleotides to mutate two or ZmPYLgenes simultaneously (Table 3). Table 3 shows that ZmPYL-F in a highpercentage of PMI positive events (transformants) contain mutations atthe intended sequences (5′-GCTCG TGATC GAGTC CTTCG/TGGTG GACGT-3′, /indicated predicted Cas9 cleavage position) targeted by gRNA-Cas9.

TABLE 3 Targeted mutagenesis and allele replacement experiments ofdifferent ZmPYL genes Number of Number of Total Total events withputative ODN(s) used for number of number of mutation(s) events withZmPYL Transformation generating targeted Number of immature PMI positiveat the target desired allele target gene vector(s) mutation (s)experiments embryos events site* change ZmPYL-D 23136 ODN-ZmPYL-Dc 57914 279 132 3 ZmPYL-D 23136, ODN-ZmPYL-Dc 2 2102 TBD TBD TBD 12672ZmPYL-D 23189 ODN-ZmPYL-Db 1 1750 TBD TBD TBD ZmPYL-E 23190 ODN-ZmPYL-Eb2 2238 60** 15 and TBD 1 and TBD ZmPYL-F 22981 ODN-ZmPYL-Fb 6 5460 80and TBD 13 and TBD TBD ZmPYL-F 22981, ODN-ZmPYL-Fb 5 7225 346 and 171and 6 and TBD with other TBD TBD (22980, 22978, 22982)** ZmPYL-F 22981ODN-ZmPYL-Fc 1 810 TBD TBD TBD ZmPYL-J 23192 ODN-ZmPYL-Jc short 1 855TBD TBD TBD ZmPYL-J 23192 ODN-ZmPYL-Jc long 1 1605 TBD TBD TBD ZmPYL-E,23190, ODN-ZmPYL-Eb, 1 1785 TBD TBD TBD ZmPYL-F 23191 ODN-ZmPYL-FcZmPYL-F, 23191 + ODN-ZmPYL-Jd-S-NT, 1 1970 TBD TBD TBD ZmPYL-J 23192ODN-ZmPYL-Fd-NT ZmPYL-F, 23191 + ODN-ZmPYL-Jd-S-NT- 1 1505 TBD TBD TBDZmPYL-J 23192 PM, ODN-ZmPYL-Fd- NT-PM

Sequencing of ZmPYL-F target region in selected mutants confirmed qPCRresults. FIG. 13 shows sequence alignment of targeted mutations inZmPYL-F mediated by gRNA-Cas9 expressed from vector 22981. Note: * Eventwith both monoallelic and/or biallelic mutations; ** These vectors(22980, 22978 or 22982) carry cassettes for expression of control gRNAs(including NGG sequence) for testing specificity of gRNA for ZmPYLgenes. # TBD, to be determined; experiments are in progress and no datais available at the moment.

5.4 Molecular Characterization of Edited ZmPYL Mutants

Leaf samples are harvested from regenerated plants in root vessels formolecular analysis or genotyping to identify plants containing mutationsat the target sequence and also containing desired sequence mutationsthat results in desired amino acid change in the ZmPYL genes. Targetedmutants can be identified using one of the following methods: (1) PCRamplification of the target region followed by restriction enzymedigestion and gel electrophoresis if the mutated sequence contains arestriction site (Lloyd A et al. 2005. Proc. Natl. Acad. Sci. USA102:2232-37; Zhang F, et al. 2010. Proc. Natl. Acad. Sci. USA107:12028-33). This method is simple, but requires the presence ofsuitable restriction site, thus cannot be used for most targets. (2) PCRamplification of the target region followed by Sanger sequencing or deepsequencing (Gross, E. et al. 1999. Hum. Genet. 105, 72-78. Shukla V K,et al. 2009. Nature 459:437-41. Townsend J A, et al. 2009. Nature459:442-45.); Sequencing approach is definitive and sensitive, but takeslonger time and throughput can be limited by capacity. (3) PCRamplification of the target region followed by denaturation, annealingand capillary electrophoresis (Li-Sucholeik X C, et al. 1999.Electrophoresis 20, 1224-1232; Larsen L A, et al. 1999. Hum. Mutat. 13,318-327) or denaturing high-performance liquid chromatography to detectbase pair changes by heteroduplex analysis (McCallum C M, et al. 2000.Nature Biotechnology 18, 455-457); these methods are limited bythroughput and the identified mutations need to be further verified bysequencing. (4) PCR amplification of the target region followed bydenaturation, heteroduplex formation/strand annealing, digestion withmismatch-specific nuclease (such as CEL1 and T7 endonuclease) and gelelectrophoresis (Oleykowski, C. A. et al. 1998. Nucleic Acids Res. 26,4597-4602. Colbert et al. 2001. Plant Physiol. 126:480-484; Lombardo A,et al. 2007. Nat. Biotechnol. 25:1298-306), for example using thecommercially available Surveyer™ nuclease assay kit (Transgenomic,Gaithersburg, Md., USA; Qiu, P., et al. 2004. BioTechniques 36,702-707). However, the gel-based assays are not as sensitive ashigh-throughput DNA sequencing and can only detect mutation withfrequency of 1% or more. All of the above 4 approaches of identifying apotential mutant in a target site are based on the presence of a newsignal in a qualitative fashion, either a new band in a gel or a newpeak in a chromatogram that is different from the wild type referencesequence.

We have developed an alternative high throughput assay method foridentification of plants with any site-directed mutation at the targetedsequences based on qPCR (Syngenta Provisional Patent Application#9207-137PR, case 80484). The method measures the reduction of the wildtype target site sequence in cells or tissues that have been treatedwith a site-directed nuclease in a quantitative fashion in comparisonwith a reference sample. Typically, a Taqman-based assay is used forquantification of the target sequence copy numbers. For detectingpotential events with desired allele replacement, an additional highthroughput end-point assay is designed and performed. In this end pointassay, signals from two MGB probes are used to determine the presence ofWT or expected mutant allele as shown in FIG. 12. Events with putativeallele replacement are selected based on both Taqman copy number assay(WT target sequence copy number) and end point assay (mutant copynumber) results. Putative events with putative allele replacement arefurther confirmed by DNA sequence analysis of amplified target locussequences. Table 4 shows the qPCR and end point assay results ofselected number of regerated maize plants generated from biolistictransformation experiment of vector 22981 (FIG. 10A-10B) co-deliveredwith oligonucleotide ODN-ZmPYL-Fb (Seq. ID.No. 402). As shown in Table4, transformation vector-specific assays were performed to determine ifthere is any transgene insertion (cCas9-01 and cPMI-09 qPCR assays).qPCR assay (ZmPYL-F cutting site) was also performed to determine thecopy number of the ZmPYL-F maize genomic target site sequence (5′-GCTCGTGATC GAGTC CTTCG/TGG-3′, SEQ ID NO:394). Finally, an end point assay(ZmPYL-F E164L) was also used to determine if plants have intendedsequence mutation (from GAG to CTG) resulting in E164L amino acidresidue change. For example, plant MZET151104A015A has a single copy oftransgene insertion (for Cas9 and PMI genes), biallelic mutations at thetarget sequence since ZmPYL-F cutting site copy call is 0 (in WT, thecopy call should be 2) and no E164L mutation. Another plantMZET151104A125A has more than 2 copies of transformation vector (22981)insertion and only one copy of the ZmPYL-F cutting site is mutated. Butplant MZET151104A125A is positive for end point assay for detectingZmPYL-F E164L mutation. This event is thus a candidate event withZmPYL-F E164L mutation. Candidate events MZET151104A125A,MZET151104A174A and MZET151104A180A in Table 4 are then furtherconfirmed by sequencing analysis of PCR-amplified ZmPYL-F genomesequences.

TABLE 4 qPCR and end point assay results of regenerated maize eventsAssays for genomic Assays for target sequence transgene vector ZmPYL-FZmPYL-F cCas9-01 cPMI-09 cutting site E164L Assay name (qPCR) (qPCR)(qPCR) (End point) (Type) Copy Copy Copy Null/Het/ Candidate Plant IDConstruct ID number number number Hom event MZET151104A015A 22981 1 1 0Null MZET151104A017A 22981 1 1 1 Null MZET151104A019A 22981 >2 >2 0 or 1Null MZET151104A021A 22981 1 1 1 Null MZET151104A125A 22981 >2 2 1 HetYes MZET151104A126A 22981 >2 >2 1 Null MZET151104A132A 22981 1 1 or 2 1or 2 Null MZET151104A138A 22981 1 1 0 Null MZET151104A141A 22981 1 or 21 0 Null MZET151104A158A 22981 >2 2 1 Null MZET151104A174A 22981 >2 >2 1Het Yes MZET151104A178A 22981 >2 1 1 Null MZET151104A180A 22981 >2 1 1Het Yes MZET151104A186A 22981 >2 >2 0 or 1 Null MZET151104A195A22981 >2 >2 0 Null MZET151104A201A 22981 0 0 1 Null

5.5 Evaluation of ZmPYL Gene Edited Mutants

ZmPYL gene edited mutants are tested as described for transgenic T6PPmaize plants (Nuccio et al., 2015, Nature Biotechnology,doi:10.1038/nbt.3277) with managed stress environment (MSE) trials.Mutant lines that show improved plant response to water deficit arefurther tested in multiple location agronomic equivalency (Ag Eq) trialswith mutant lines grown alongside control plants and using acheckerboard plot layout.

PYL-E V89A (SEQ ID NO: 389)Met Val Gly Leu Val Gly Gly Ser Thr Ala Arg Ala Glu His Val Val 1               5                  10                  15Ala Asn Ala Gly Gly Glu Ala Glu Tyr Val Arg Arg Met His Arg His            20                  25                  30Ala Pro Thr Glu His Gln Cys Thr Ser Thr Leu Val Lys His Ile Lys        35                  40                  45Ala Pro Val His Leu Val Trp Glu Leu Val Arg Arg Phe Asp Gln Pro    50                  55                  60Gln Arg Tyr Lys Pro Phe Val Arg Asn Cys Val Val Arg Gly Asp Gln65                  70                  75                  80Leu Glu Val Gly Ser Leu Arg Asp Ala Asn Val Lys Thr Gly Leu Pro                85                  90                  95Ala Thr Thr Ser Thr Glu Arg Leu Glu Gln Leu Asp Asp Asp Leu His            100                 105                 110Ile Leu Gly Val Lys Phe Val Gly Gly Asp His Arg Leu Gln Asn Tyr        115                 120                 125Ser Ser Ile Ile Thr Val His Pro Glu Ser Ile Asp Gly Arg Pro Gly    130                 135                 140Thr Leu Val Ile Glu Ser Phe Val Val Asp Val Pro Asp Gly Asn Thr145                 150                 155                 160Lys Asp Glu Thr Cys Tyr Phe Val Glu Ala Val Ile Lys Cys Asn Leu                165                 170                 175Asn Ser Leu Ala Glu Val Ser Glu Gln Leu Ala Val Glu Ser Pro Thr            180                 185                 190Ser Leu Ile Asp Gln         195 PYL-E V89A E149L (SEQ ID NO: 390)Met Val Gly Leu Val Gly Gly Ser Thr Ala Arg Ala Glu His Val Val 1               5                  10                  15Ala Asn Ala Gly Gly Glu Ala Glu Tyr Val Arg Arg Met His Arg His            20                  25                  30Ala Pro Thr Glu His Gln Cys Thr Ser Thr Leu Val Lys His Ile Lys        35                  40                  45Ala Pro Val His Leu Val Trp Glu Leu Val Arg Arg Phe Asp Gln Pro    50                  55                  60Gln Arg Tyr Lys Pro Phe Val Arg Asn Cys Val Val Arg Gly Asp Gln65                  70                  75                  80Leu Glu Val Gly Ser Leu Arg Asp Ala Asn Val Lys Thr Gly Leu Pro                85                  90                  95Ala Thr Thr Ser Thr Glu Arg Leu Glu Gln Leu Asp Asp Asp Leu His            100                 105                 110Ile Leu Gly Val Lys Phe Val Gly Gly Asp His Arg Leu Gln Asn Tyr        115                 120                 125Ser Ser Ile Ile Thr Val His Pro Glu Ser Ile Asp Gly Arg Pro Gly    130                 135                 140Thr Leu Val Ile Leu Ser Phe Val Val Asp Val Pro Asp Gly Asn Thr145                 150                 155                 160Lys Asp Glu Thr Cys Tyr Phe Val Glu Ala Val Ile Lys Cys Asn Leu                165                 170                 175Asn Ser Leu Ala Glu Val Ser Glu Gln Leu Ala Val Glu Ser Pro Thr            180                 185                 190Ser Leu Ile Asp Gln         195 PYL-E V89I E149L (SEQ ID NO: 391)Met Val Gly Leu Val Gly Gly Ser Thr Ala Arg Ala Glu His Val Val 1               5                  10                  15Ala Asn Ala Gly Gly Glu Ala Glu Tyr Val Arg Arg Met His Arg His            20                  25                  30Ala Pro Thr Glu His Gln Cys Thr Ser Thr Leu Val Lys His Ile Lys        35                  40                  45Ala Pro Val His Leu Val Trp Glu Leu Val Arg Arg Phe Asp Gln Pro    50                  55                  60Gln Arg Tyr Lys Pro Phe Val Arg Asn Cys Val Val Arg Gly Asp Gln65                  70                  75                  80Leu Glu Val Gly Ser Leu Arg Asp Ile Asn Val Lys Thr Gly Leu Pro                85                  90                  95Ala Thr Thr Ser Thr Glu Arg Leu Glu Gln Leu Asp Asp Asp Leu His            100                 105                 110Ile Leu Gly Val Lys Phe Val Gly Gly Asp His Arg Leu Gln Asn Tyr        115                 120                 125Ser Ser Ile Ile Thr Val His Pro Glu Ser Ile Asp Gly Arg Pro Gly    130                 135                 140Thr Leu Val Ile Leu Ser Phe Val Val Asp Val Pro Asp Gly Asn Thr145                 150                 155                 160Lys Asp Glu Thr Cys Tyr Phe Val Glu Ala Val Ile Lys Cys Asn Leu                165                 170                 175Asn Ser Leu Ala Glu Val Ser Glu Gln Leu Ala Val Glu Ser Pro Thr            180                 185                 190Ser Leu Ile Asp Gln         195 PYL-E V89Y E149L (SEQ ID NO: 392)Met Val Gly Leu Val Gly Gly Ser Thr Ala Arg Ala Glu His Val Val 1               5                  10                  15Ala Asn Ala Gly Gly Glu Ala Glu Tyr Val Arg Arg Met His Arg His            20                  25                  30Ala Pro Thr Glu His Gln Cys Thr Ser Thr Leu Val Lys His Ile Lys        35                  40                  45Ala Pro Val His Leu Val Trp Glu Leu Val Arg Arg Phe Asp Gln Pro    50                  55                  60Gln Arg Tyr Lys Pro Phe Val Arg Asn Cys Val Val Arg Gly Asp Gln65                  70                  75                  80Leu Glu Val Gly Ser Leu Arg Asp Tyr Asn Val Lys Thr Gly Leu Pro                85                  90                  95Ala Thr Thr Ser Thr Glu Arg Leu Glu Gln Leu Asp Asp Asp Leu His            100                 105                 110Ile Leu Gly Val Lys Phe Val Gly Gly Asp His Arg Leu Gln Asn Tyr        115                 120                 125Ser Ser Ile Ile Thr Val His Pro Glu Ser Ile Asp Gly Arg Pro Gly    130                 135                 140Thr Leu Val Ile Leu Ser Phe Val Val Asp Val Pro Asp Gly Asn Thr145                 150                 155                 160Lys Asp Glu Thr Cys Tyr Phe Val Glu Ala Val Ile Lys Cys Asn Leu                165                 170                 175Asn Ser Leu Ala Glu Val Ser Glu Gln Leu Ala Val Glu Ser Pro Thr            180                 185                 190Ser Leu Ile Asp Gln         195 ODN-ZmPYL-Dc (SEQ ID NO: 398)AGGTC ATCGA CGGCC GGCCA GGGAC GCTCG TCATC CTGTC ATTCG TCGTCGACGT CCCCG ACGGC AACAC CAAGG ODN-ZmPYL-Dd-NT (SEQ ID NO: 399)CCTTG GTGTT GCCGT CGGGG ACGTC GACGA CGAAT GACAG GATGA CGAGCGTCCC TGGCC GGCCG TCGAT GACCT ODN-ZmPYL-Dd-NT-PM (SEQ ID NO: 400)C*C*T*T GGTGT TGCCG TCGGG GACGT CGACG ACGAA TGACA GGATG ACGAGCGTCC CTGGC CGGCC GTCGA TGA*C*C *T*denotes phosphorothioate modification ODN-ZmPYL-Db (SEQ ID NO: 401)CCATC CTCAC CGTCC ACCCG GAGGT CATCG ACGGC CGACC AGGGA CGCTCGTCAT CCTGT CCTTC GTCGT CGACG TCCCC GACGG CAA ODN-ZmPYL-Fa(SEQ ID NO: 402)CGACG GCCGA CCGGG GACGC TCGTG ATCCT GTCCT TCGTG GTGGA CGTCC CCGAC GGCAAODN-ZmPYL-Fb (SEQ ID NO: 403)CGACG GCCGA CCGGG GACGC TCGTG ATCCT GTCCT TCGTA GTGGA CGTCC CCGAC GGCAAODN-ZmPYL-Fc (SEQ ID NO: 404)AGGTC ATCGA CGGCC GACCG GGGAC GCTCG TGATC CTGTC CTTCG TAGTGGACGT CCCCG ACGGC AACAC CAAGG AC ODN-ZmPYL-Fd-NT (SEQ ID NO: 405)GTCCT TGGTG TTGCC GTCGG GGACG TCCAC TACGA AGGAC AGGAT CACGAGCGTC CCCGG TCGGC CGTCG ATGAC CT ODN-ZmPYL-Fd-NT-PM (SEQ ID NO: 406)G*T*C*CT TGGTG TTGCC GTCGG GGACG TCCAC TACGA AGGAC AGGAT CACGAGCGTC CCCGG TCGGC CGTCG ATGA*C* C*T*denotes phosphorothioate modification ODN-ZmPYL-Jc short(SEQ ID NO: 407)CACCG AGTTC CAGCC GGGCC CCTAC TGCGT CGTGC TCCTG TCCTA CGTCGTCGAC GTCCC CGACG GCA ODN-ZmPYL-Jc short-NT (SEQ ID NO: 408)TGCCG TCGGG GACGT CGACG ACGTA GGACA GGAGC ACGAC GCAGT AGGGGCCCGG CTGGA ACTCG GTG ODN-ZmPYL-Jc short-NT-PM (SEQ ID NO: 409)T*G*C*CG TCGGG GACGT CGACG ACGTA GGACA GGAGC ACGAC GCAGT AGGGGCCCGG CTGGA ACTCG *G*T*G *denotes phosphorothioate modificationODN-ZmPYL-Jc long (SEQ ID NO: 410)TCACC TCCGT CACCG AGTTC CAGCC GGGCC CCTAC TGCGT CGTGC TCCTGTCCTA CGTCG TCGAC GTCCC CGACG GCAAC ACCGA GGA

It is understood that the examples and embodiments described herein arefor illustrative purposes only and that various modifications or changesin light thereof will be suggested to persons skilled in the art and areto be included within the spirit and purview of this application andscope of the appended claims. All publications, patents, and patentapplications cited herein are hereby incorporated by reference in theirentirety for all purposes.

What is claimed is:
 1. An isolated nucleic acid comprising apolynucleotide encoding a mutated PYR/PYL receptor polypeptidecomprising an amino acid substitution corresponding to the amino acidF61, V81, I110, E141, and A160 in PYR1 as set forth in SEQ ID NO:1,wherein the mutated PYR/PYL receptor has increased sensitivity toabscisic acid compared to a control PYR/PYL receptor lacking thesubstitution.
 2. The isolated nucleic acid of claim 1, wherein thePYR/PYL receptor polypeptide comprises an amino acid substitutioncorresponding to the amino acid F61.
 3. The isolated nucleic acid ofclaim 2, wherein the amino acid substitution is selected from L and M.4. The isolated nucleic acid of claim 1, wherein the PYR/PYL receptorpolypeptide comprises an amino acid substitution corresponding to theamino acid V81.
 5. The isolated nucleic acid of claim 4, wherein theamino acid substitution is selected from I and Y.
 6. The isolatednucleic acid of claim 1, wherein the PYR/PYL receptor polypeptidecomprises an amino acid substitution corresponding to the amino acidI110.
 7. The isolated nucleic acid of claim 6, wherein the amino acidsubstitution is selected from C and S.
 8. The isolated nucleic acid ofclaim 1, wherein the PYR/PYL receptor polypeptide comprises an aminoacid substitution corresponding to the amino acid E141.
 9. The isolatednucleic acid of claim 8, wherein the amino acid substitution is selectedfrom C, I, L, M, N, T, V, W, and Y.
 10. The isolated nucleic acid ofclaim 1, wherein the PYR/PYL receptor polypeptide comprises an aminoacid substitution corresponding to the amino acid A160.
 11. The isolatednucleic acid of claim 8, wherein the amino acid substitution is selectedfrom C, I, and V.
 12. The isolated nucleic acid of claim 1, wherein themutated PYR/PYL receptor polypeptide is substantially identical to anyof SEQ ID NOs:1-119 or SEQ ID NOs:155-361 or comprises any of SEQ IDNOs: 120-123.
 13. The isolated nucleic acid of claim 1, wherein thepolynucleotide encodes a fusion protein, the fusion protein comprisingthe mutated PYR/PYL receptor polypeptide and a fusion partner protein.14. The isolated nucleic acid of claim 13, wherein the fusion partnerprotein is a transcriptional activation or modulation domain.
 15. Theisolated nucleic acid of claim 14, wherein the transcriptional activatoris VP16 or VP64.
 16. The isolated nucleic acid of claim 13, wherein thefusion protein further comprises a nuclear localization signal sequence.17. A cell comprising a heterologous polynucleotide of claim
 1. 18. Thecell of claim 17, wherein the cell is a non-plant eukaryotic cell.
 19. Aplant comprising the polynucleotide of claim
 1. 20. A plant comprisingan in situ mutated PYR/PYL receptor polypeptide comprising an amino acidsubstitution corresponding to the amino acid F61, V81, I110, E141, andA160 in PYR1 as set forth in SEQ ID NO:1, wherein the mutated PYR/PYLreceptor polypeptide has increased sensitivity to abscisic acid comparedto a control PYR/PYL receptor lacking the substitution.
 21. Anexpression cassette comprising a promoter operably linked to thepolynucleotide of claim 1, wherein introduction of the expressioncassette into a plant results in the plant having increased sensitivityto abscisic acid compared to a control plant lacking the expressioncassette.
 22. The expression cassette of claim 21, wherein the promoteris heterologous to the polynucleotide.
 23. The expression cassette ofclaim 21, wherein the promoter is inducible.
 24. The expression cassetteof claim 21, wherein the promoter is a stress-inducible promoter.
 25. Anexpression vector comprising the expression cassette of claim
 21. 26. Aplant comprising the expression cassette of claim 21, wherein the planthas increased sensitivity to abscisic acid compared to a control plantlacking the expression cassette.
 27. A plant cell from the plant ofclaim
 19. 28. A seed, flower, leaf, fruit, processed food, or foodingredient from the plant of claim
 19. 29. A method of producing a planthaving increased sensitivity to abscisic acid, the method comprising:introducing the expression cassette of claim 21 into a plurality ofplants; and selecting a plant that expresses the polynucleotide from theplurality of plants.
 30. A method of producing a plant having increasedsensitivity to abscisic acid, the method comprising: introducing amutation into a polynucleotide encoding a PYR/PYL polypeptide, whereinthe mutation results in the polynucleotide of claim
 1. 31. The method ofclaim 30, wherein the introducing occurs in situ in the genome of aplant cell.
 32. The method of claim 31, wherein the introducingcomprises clustered regularly interspaced short palindromic repeats(CRISPR)/Cas genome editing.
 33. A guide ribonucleic acid (gRNA)comprising: a) a CRISPR ribonucleic acid (crRNA) that is substantiallyidentical to SEQ ID NOS: 363, 364, 365, 366, 367 or 369; and b) atransacting ribonucleic acid (tracRNA), wherein the PYR/PYL mutationtarget site comprises a nucleic acid that encodes for V89 of PYL-E orE149 of PYL-E.